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Kyogoku D, Yamaguchi R. Males and females contribute differently to the evolution of habitat segregation driven by hybridization. J Evol Biol 2023; 36:515-528. [PMID: 36721300 DOI: 10.1111/jeb.14156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 12/27/2022] [Accepted: 01/11/2023] [Indexed: 02/02/2023]
Abstract
Costly heterospecific mating interactions, such as hybridization, select for prezygotic reproductive isolation. One of the potential traits responding to the selection arising from maladaptive hybridization is habitat preference, whose divergence results in interspecific habitat segregation. Theoretical studies have so far assumed that habitat preference is a sexually shared trait. However, male and female habitat preferences can experience different selection pressures. Here, by combining analytical and simulation approaches, we theoretically examine the evolution of sex-specific habitat preferences. Habitat segregation can have demographic consequences, potentially generating eco-evolutionary dynamics. We thus explicitly consider demography in the simulation model. We also vary the degrees of species discrimination to examine how mate choice influences the evolution of habitat preferences. Results show that both sexes can reduce hybridisation risk by settling in the habitats where abundant conspecific mates reside. However, when females can discriminate species, excess conspecific male aggregation intensifies male-male competition for mating opportunities, posing an obstacle to conspecific aggregation. Meanwhile, conspecific female aggregation attracts conspecific males, by offering the mating opportunity. Therefore, under effective species discrimination, females play a leading role in initiating habitat use divergence. Simulations typically result in either the coexistence with established habitat segregation or the extinction of one of the species. The former result is especially likely when the species differ to some extent in habitat preferences upon secondary contact. Our results disentangle the selection pressures acting on male and female habitat preferences, deepening our understanding of the evolutionary process of habitat segregation due to hybridization.
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Affiliation(s)
| | - Ryo Yamaguchi
- Department of Advanced Transdisciplinary Science, Hokkaido University, Sapporo, Japan.,Department of Zoology & Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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2
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Machida Y, Takahashi H, Tsuruta T, Goto A. Effect of salinity on nest building behaviour in the nine-spined stickleback Pungitius sinensis. J Fish Biol 2023; 102:516-519. [PMID: 36321928 DOI: 10.1111/jfb.15264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
The authors evaluated the adaptability of male nine-spined sticklebacks (Pungitius sinensis) at three salinity levels (0, 5 and 10 psu) by comparing nest building success rates with nest structures. Successful nest building decreased as salinity increased. In addition, nests built in fresh water (i.e., 0 psu) were glued together, whereas those built in brackish water (5 and 10 psu) broke easily and fell from the nest site to the gravel bottom. Based on these findings, the authors suggest that P. sinensis adapts to freshwater environments.
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Affiliation(s)
| | - Hiroshi Takahashi
- Department of Applied Aquabiology, National Fisheries University, Yamaguchi, Japan
| | - Tetsuya Tsuruta
- Department of Environmental Science and Technology, Faculty of Design Technology, Osaka Sangyo University, Osaka, Japan
| | - Akira Goto
- Field Science Center for Northern Biosphere, Hokkaido University, Hokkaido, Japan
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3
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Harenčár JG, Ávila‐Lovera E, Goldsmith GR, Chen GF, Kay KM. Flexible drought deciduousness in a neotropical understory herb. Am J Bot 2022; 109:1262-1272. [PMID: 35862815 PMCID: PMC9545341 DOI: 10.1002/ajb2.16037] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 06/21/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
PREMISE Adaptive divergence across environmental gradients is a key driver of speciation. Precipitation seasonality gradients are common in the tropics, yet drought adaptation is nearly unexplored in neotropical understory herbs. Here, we examined two recently diverged neotropical spiral gingers, one adapted to seasonal drought and one reliant on perennial water, to uncover the basis of drought adaptation. METHODS We combined ecophysiological trait measurements in the field and greenhouse with experimental and observational assessments of real-time drought response to determine how Costus villosissimus (Costaceae) differs from C. allenii to achieve drought adaptation. RESULTS We found that drought-adapted C. villosissimus has several characteristics indicating flexible dehydration avoidance via semi-drought-deciduousness and a fast economic strategy. Although the two species do not differ in water-use efficiency, C. villosissimus has a more rapid growth rate, lower leaf mass per area, lower stem density, higher leaf nitrogen, and a strong trend of greater light-saturated photosynthetic rates. These fast economic strategy traits align with both field-based observations and experimental dry-down results. During drought, C. villosissimus displays facultative drought-deciduousness, losing lower leaves during the dry season and rapidly growing new leaves in the wet season. CONCLUSIONS We revealed a drought adaptation strategy that has not, to our knowledge, previously been documented in tropical herbs. This divergent drought adaptation evolved recently and is an important component of reproductive isolation between C. villosissimus and C. allenii, indicating that adaptive shifts to survive seasonal drought may be an underappreciated axis of neotropical understory plant diversification.
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Affiliation(s)
- Julia G. Harenčár
- Ecology and Evolutionary Biology DepartmentUniversity of California, Santa CruzSanta CruzCA95060USA
| | - Eleinis Ávila‐Lovera
- Smithsonian Tropical Research InstituteApartado Postal 0843‐03092Panamá, República de Panamá
- Schmid College of Science and TechnologyChapman UniversityOrangeCA92866USA
| | | | - Grace F. Chen
- Department of BiologyEast Carolina UniversityGreenvilleNC27858USA
| | - Kathleen M. Kay
- Ecology and Evolutionary Biology DepartmentUniversity of California, Santa CruzSanta CruzCA95060USA
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4
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Ribardière A, Pabion E, Coudret J, Daguin-Thiébaut C, Houbin C, Loisel S, Henry S, Broquet T. Sexual isolation with and without ecological isolation in marine isopods Jaera albifrons and J. praehirsuta. J Evol Biol 2019; 34:33-48. [PMID: 31631475 DOI: 10.1111/jeb.13559] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/26/2019] [Accepted: 10/17/2019] [Indexed: 01/26/2023]
Abstract
Sexual barriers associated with mate choice are often found to be associated with some level of ecological isolation between species. The independence and relative strength of sexual isolation are thus difficult to assess. Here, we take advantage of a pair of marine isopod species (Jaera albifrons and J. praehirsuta) that show sexual isolation and coexist in populations where they share the same microhabitat or not (i.e. without or with ecological isolation). We estimated the strength of sexual isolation between J. albifrons and J. praehirsuta using no-choice trials and a multiple-choice experimental population. We found that sexual isolation is strong in both the presence and the absence of ecological isolation, but that it is asymmetric and fails to prevent interspecific gene flow entirely. First-generation intrinsic post-zygotic barriers were low, and there was no sexual isolation within J. praehirsuta across habitats. The J. albifrons/J. praehirsuta species pair thus provides an example where the role of sexual isolation as a barrier to gene flow (a) does not depend upon current ecological isolation, (b) seems to have evolved independently of local ecological conditions, but (c) is insufficient to complete speciation entirely on its own.
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Affiliation(s)
- Ambre Ribardière
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | - Elsa Pabion
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | - Jérôme Coudret
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | | | - Céline Houbin
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France.,FR2424, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | - Stéphane Loisel
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | - Sébastien Henry
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France.,FR2424, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
| | - Thomas Broquet
- UMR 7144, Station Biologique de Roscoff, CNRS & Sorbonne Université, Roscoff, France
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5
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Costanzi J, Steifetten Ø. Island biogeography theory explains the genetic diversity of a fragmented rock ptarmigan ( Lagopus muta) population. Ecol Evol 2019; 9:3837-3849. [PMID: 31015970 PMCID: PMC6468070 DOI: 10.1002/ece3.5007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 01/31/2019] [Accepted: 02/04/2019] [Indexed: 01/20/2023] Open
Abstract
The island biogeography theory is one of the major theories in ecology, and its applicability to natural systems is well documented. The core model of the theory, the equilibrium model of island biogeography, predicts that species diversity on an island is positively related to the size of the island, but negatively related by the island's distance to the mainland. In recent years, ecologists have begun to apply this model when investigating genetic diversity, arguing that genetic and species diversity might be influenced by similar ecological processes. However, most studies have focused on oceanic islands, but knowledge on how the theory applies to islands located on the mainland (e.g., mountain islands, forest islands) is scarce. In this study, we examined how the size and degree of isolation of mountain islands would affect the genetic diversity of an alpine bird, the rock ptarmigan (Lagopus muta). Within our study area, we defined the largest contiguous mountain area as the mainland, while smaller mountains surrounding the mainland were defined as islands. We found that the observed heterozygosity (H o) was significantly higher, and the inbreeding coefficient (F is) significantly lower, on the mainland compared to islands. There was a positive significant relationship between the unbiased expected heterozygosity (H n.b.) and island size (log km2), but a negative significant relationship between H o and the cost distance to the mainland. Our results are consistent with the equilibrium model of island biogeography and show that the model is well suited for investigating genetic diversity among islands, but also on islands located on the mainland.
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Affiliation(s)
- Jean‐Marc Costanzi
- Department of Natural Sciences and Environmental HealthUniversity of South‐Eastern NorwayBø i TelemarkNorway
| | - Øyvind Steifetten
- Department of Natural Sciences and Environmental HealthUniversity of South‐Eastern NorwayBø i TelemarkNorway
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6
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Ottens K, Winkler IS, Lewis ML, Scheffer SJ, Gomes-Costa GA, Condon MA, Forbes AA. Genetic differentiation associated with host plants and geography among six widespread species of South American Blepharoneura fruit flies (Tephritidae). J Evol Biol 2017; 30:696-710. [PMID: 28106948 DOI: 10.1111/jeb.13043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 01/12/2017] [Accepted: 01/13/2017] [Indexed: 11/29/2022]
Abstract
Tropical herbivorous insects are astonishingly diverse, and many are highly host-specific. Much evidence suggests that herbivorous insect diversity is a function of host plant diversity; yet, the diversity of some lineages exceeds the diversity of plants. Although most species of herbivorous fruit flies in the Neotropical genus Blepharoneura are strongly host-specific (they deposit their eggs in a single host plant species and flower sex), some species are collected from multiple hosts or flowers and these may represent examples of lineages that are diversifying via changes in host use. Here, we investigate patterns of diversification within six geographically widespread Blepharoneura species that have been collected and reared from at least two host plant species or host plant parts. We use microsatellites to (1) test for evidence of local genetic differentiation associated with different sympatric hosts (different plant species or flower sexes) and (2) examine geographic patterns of genetic differentiation across multiple South American collection sites. In four of the six fly species, we find evidence of local genetic differences between flies collected from different hosts. All six species show evidence of geographic structure, with consistent differences between flies collected in the Guiana Shield and flies collected in Amazonia. Continent-wide analyses reveal - in all but one instance - that genetically differentiated flies collected in sympatry from different host species or different sex flowers are not one another's closest relatives, indicating that genetic differences often arise in allopatry before, or at least coincident with, the evolution of novel host use.
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Affiliation(s)
- K Ottens
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - I S Winkler
- Department of Biology, Cornell College, Mount Vernon, IA, USA
| | - M L Lewis
- Systematic Entomology Laboratory, Agricultural Research Service - U.S. Department of Agriculture (ARS-USDA), Beltsville, MD, USA
| | - S J Scheffer
- Systematic Entomology Laboratory, Agricultural Research Service - U.S. Department of Agriculture (ARS-USDA), Beltsville, MD, USA
| | - G A Gomes-Costa
- Programa de Pós-Graduação em Biologia Vegetal, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil
| | - M A Condon
- Department of Biology, Cornell College, Mount Vernon, IA, USA
| | - A A Forbes
- Department of Biology, University of Iowa, Iowa City, IA, USA
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Forbes AA, Devine SN, Hippee AC, Tvedte ES, Ward AKG, Widmayer HA, Wilson CJ. Revisiting the particular role of host shifts in initiating insect speciation. Evolution 2017; 71:1126-1137. [PMID: 28052326 DOI: 10.1111/evo.13164] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 12/30/2016] [Indexed: 12/31/2022]
Abstract
The notion that shifts to new hosts can initiate insect speciation is more than 150 years old, yet widespread conflation with paradigms of sympatric speciation has led to confusion about how much support exists for this hypothesis. Here, we review 85 insect systems and evaluate the relationship between host shifting, reproductive isolation, and speciation. We sort insects into five categories: (1) systems in which a host shift has initiated speciation; (2) systems in which a host shift has made a contribution to speciation; (3) systems in which a host shift has caused the evolution of new reproductive isolating barriers; (4) systems with host-associated genetic differences; and (5) systems with no evidence of host-associated genetic differences. We find host-associated genetic structure in 65 systems, 43 of which show that host shifts have resulted in the evolution of new reproductive barriers. Twenty-six of the latter also support a role for host shifts in speciation, including eight studies that definitively support the hypothesis that a host shift has initiated speciation. While this review is agnostic as to the fraction of all insect speciation events to which host shifts have contributed, it clarifies that host shifts absolutely can and do initiate speciation.
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Affiliation(s)
- Andrew A Forbes
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
| | - Sara N Devine
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
| | - Alaine C Hippee
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
| | - Eric S Tvedte
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
| | - Anna K G Ward
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
| | | | - Caleb J Wilson
- Department of Biology, University of Iowa, Iowa City, Iowa, 52242
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Coudrain V, Rittiner S, Herzog F, Tinner W, Entling MH. Landscape distribution of food and nesting sites affect larval diet and nest size, but not abundance of Osmia bicornis. Insect Sci 2016; 23:746-753. [PMID: 25973721 DOI: 10.1111/1744-7917.12238] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/23/2015] [Indexed: 06/04/2023]
Abstract
Habitat fragmentation is a major threat for beneficial organisms and the ecosystem services they provide. Multiple-habitat users such as wild bees depend on both nesting and foraging habitat. Thus, they may be affected by the fragmentation of at least two habitat types. We investigated the effects of landscape-scale amount of and patch isolation from both nesting habitat (woody plants) and foraging habitat (specific pollen sources) on the abundance and diet of Osmia bicornis L. Trap-nests of O. bicornis were studied in 30 agricultural landscapes of the Swiss Plateau. Nesting and foraging habitats were mapped in a radius of 500 m around the sites. Pollen composition of larval diet changed as isolation to the main pollen source, Ranunculus, increased, suggesting that O. bicornis adapted its foraging strategy in function of the nest proximity to main pollen sources. Abundance of O. bicornis was neither related to isolation or amount of nesting habitat nor to isolation or abundance of food plants. Surprisingly, nests of O. bicornis contained fewer larvae in sites at forest edge compared to isolated sites, possibly due to higher parasitism risk. This study indicates that O. bicornis can nest in a variety of situations by compensating scarcity of its main larval food by exploiting alternative food sources.
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Affiliation(s)
- Valérie Coudrain
- Research Station ART, Zürich, CH-8046, Switzerland.
- Institute of Ecology and Evolution, University of Bern, Bern, CH-3012, Switzerland.
- Institute for Environmental Sciences, University of Koblenz-Landau, Landau/Pfalz, D-76829, Germany.
| | - Sarah Rittiner
- Institute of Ecology and Evolution, University of Bern, Bern, CH-3012, Switzerland
| | - Felix Herzog
- Research Station ART, Zürich, CH-8046, Switzerland
| | - Willy Tinner
- Institute of Plant Sciences and Oeschger Centre for Climate Change Research, University of Bern, Bern, CH-3013, Switzerland
| | - Martin H Entling
- Institute for Environmental Sciences, University of Koblenz-Landau, Landau/Pfalz, D-76829, Germany
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Kautt AF, Machado-Schiaffino G, Torres-Dowdall J, Meyer A. Incipient sympatric speciation in Midas cichlid fish from the youngest and one of the smallest crater lakes in Nicaragua due to differential use of the benthic and limnetic habitats? Ecol Evol 2016; 6:5342-57. [PMID: 27551387 PMCID: PMC4984508 DOI: 10.1002/ece3.2287] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/08/2016] [Accepted: 06/09/2016] [Indexed: 12/21/2022] Open
Abstract
Understanding how speciation can occur without geographic isolation remains a central objective in evolutionary biology. Generally, some form of disruptive selection and assortative mating are necessary for sympatric speciation to occur. Disruptive selection can arise from intraspecific competition for resources. If this competition leads to the differential use of habitats and variation in relevant traits is genetically determined, then assortative mating can be an automatic consequence (i.e., habitat isolation). In this study, we caught Midas cichlid fish from the limnetic (middle of the lake) and benthic (shore) habitats of Crater Lake Asososca Managua to test whether some of the necessary conditions for sympatric speciation due to intraspecific competition and habitat isolation are given. Lake As. Managua is very small (<900 m in diameter), extremely young (maximally 1245 years of age), and completely isolated. It is inhabited by, probably, only a single endemic species of Midas cichlids, Amphilophus tolteca. We found that fish from the limnetic habitat were more elongated than fish collected from the benthic habitat, as would be predicted from ecomorphological considerations. Stable isotope analyses confirmed that the former also exhibit a more limnetic lifestyle than the latter. Furthermore, split‐brood design experiments in the laboratory suggest that phenotypic plasticity is unlikely to explain much of the observed differences in body elongation that we observed in the field. Yet, neutral markers (microsatellites) did not reveal any genetic clustering in the population. Interestingly, demographic inferences based on RAD‐seq data suggest that the apparent lack of genetic differentiation at neutral markers could simply be due to a lack of time, as intraspecific competition may only have begun a few hundred generations ago.
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Affiliation(s)
- Andreas F Kautt
- Department of Biology University of Konstanz Universitätsstrasse 10 78457 Konstanz Germany
| | | | - Julian Torres-Dowdall
- Department of Biology University of Konstanz Universitätsstrasse 10 78457 Konstanz Germany
| | - Axel Meyer
- Department of Biology University of Konstanz Universitätsstrasse 10 78457 Konstanz Germany
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10
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Koelling VA, Mauricio R. Genetic factors associated with mating system cause a partial reproductive barrier between two parapatric species of leavenworthia (brassicaceae). Am J Bot 2010; 97:412-22. [PMID: 20526457 PMCID: PMC2879664 DOI: 10.3732/ajb.0900184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Reproductive barriers play a major role in the origin and maintenance of biodiversity by restricting gene flow between species. Although both pre- and postzygotic barriers often isolate species, prezygotic barriers are thought to contribute more to reproductive isolation. We investigated possible reproductive barriers between Leavenworthia alabamica and L. crassa, parapatric species with high morphological and ecological similarity and the ability to hybridize. Using greenhouse and field experiments, we tested for habitat isolation and genetic incompatibilities. From controlled crosses, we identified unilateral incompatibility (a partial prezygotic barrier associated with the self-incompatibility system), but no evidence of other genetic incompatibilities. We found a small reduction in pollen viability of F(1) hybrids and early germination of F(1), F(2), and BC hybrids relative to L. alabamica and L. crassa in a common garden experiment, but the effect on fitness was not tested. Field studies of hybrid pollen viability and germination are needed to determine if they contribute to reproductive isolation. In a reciprocal transplant, we found no evidence of habitat isolation or reduced hybrid survival (from seedling to adult stage) or reproduction. These data suggest unilateral incompatibility partially reproductively isolates L. alabamica and L. crassa, but no other reproductive barriers could be detected.
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Affiliation(s)
- Vanessa A. Koelling
- Department of Genetics, University of Georgia, Athens, Georgia 30602-7223 USA
| | - Rodney Mauricio
- Department of Genetics, University of Georgia, Athens, Georgia 30602-7223 USA
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Aegisdóttir HH, Kuss P, Stöcklin J. Isolated populations of a rare alpine plant show high genetic diversity and considerable population differentiation. Ann Bot 2009; 104:1313-22. [PMID: 19797423 PMCID: PMC2778390 DOI: 10.1093/aob/mcp242] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Gene flow and genetic variability within and among alpine plant populations can be greatly influenced by the steep environmental gradients and heterogeneous topography of alpine landscapes. In this study, the effects are examined of natural isolation of alpine habitats on genetic diversity and geographic structure in populations of C. thyrsoides, a rare and isolated European Alpine monocarpic perennial with limited seed dispersal capacity. METHODS Molecular diversity was analysed for 736 individuals from 32 populations in the Swiss Alps and adjacent Jura mountains using five polymorphic microsatellite loci. Pollen flow was estimated using pollen grain-sized fluorescent powder. In addition, individual-based Bayesian approaches were applied to examine population structure. KEY RESULTS High within-population genetic diversity (H(E) = 0.76) and a relatively low inbreeding coefficient (F(IS) = 0.022) were found. Genetic differentiation among populations measured with a standardized measure was considerable (G'(ST) = 0.53). A significant isolation-by-distance relationship was found (r = 0.62, P < 0.001) and a significant geographic sub-structure, coinciding with proposed postglacial migration patterns. Altitudinal location and size of populations did not influence molecular variation. Direct measures of pollen flow revealed that insect-mediated pollen dispersal was restricted to short distances within a population. CONCLUSIONS The natural isolation of suitable habitats for C. thyrsoides restricts gene flow among the populations as expected for a monocarpic species with very limited seed dispersal capacities. The observed high within-population genetic diversity in this rare monocarpic perennial is best explained by its outcrossing behaviour, long-lived individuals and overlapping generations. Despite the high within-population genetic diversity, the considerable genetic differentiation and the clear western-eastern differentiation in this species merits consideration in future conservation efforts.
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12
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Medrano M, Herrera CM. Geographical structuring of genetic diversity across the whole distribution range of Narcissus longispathus, a habitat-specialist, Mediterranean narrow endemic. Ann Bot 2008; 102:183-94. [PMID: 18556752 PMCID: PMC2712358 DOI: 10.1093/aob/mcn086] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
BACKGROUND AND AIMS High mountain ranges of the Mediterranean Basin harbour a large number of narrowly endemic plants. In this study an investigation is made of the levels and partitioning of genetic diversity in Narcissus longispathus, a narrow endemic of south-eastern Spanish mountains characterized by a naturally fragmented distribution due to extreme specialization on a rare habitat type. By using dense sampling of populations across the species' whole geographical range, genetic structuring at different geographical scales is also examined. METHODS Using horizontal starch-gel electrophoresis, allozyme variability was screened at 19 loci for a total of 858 individuals from 27 populations. The data were analysed by means of standard statistical approaches in order to estimate gene diversity and the genetic structure of the populations. KEY RESULTS Narcissus longispathus displayed high levels of genetic diversity and extensive diversification among populations. At the species level, the percentage of polymorphic loci was 68 %, with average values of 2.1, 0.11 and 0.14 for the number of alleles per locus, observed heterozygosity and expected heterozygosity, respectively. Southern and more isolated populations tended to have less genetic variability than northern and less-isolated populations. A strong spatial patterning of genetic diversity was found at the various spatial scales. Gene flow/drift equilibrium occurred over distances <4 km. Beyond that distance divergence was relatively more influenced by drift. The populations studied seem to derive from three panmictic units or 'gene pools', with levels of admixture being greatest in the central and south-eastern portions of the species' range. CONCLUSIONS In addition to documenting a case of high genetic diversity in a narrow endemic plant with naturally fragmented populations, the results emphasize the need for dense population sampling and examination of different geographical scales for understanding population genetic structure in habitat specialists restricted to ecological islands.
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Affiliation(s)
- Mónica Medrano
- Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Avenida de María Luisa s/n, E-41013, Sevilla, Spain.
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