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Aulacaspis yasumatsui Invasion Reduced Cycas micronesica Microstrobilus Size and Pollinator Brood Site Competence. INSECTS 2021; 12:insects12111023. [PMID: 34821823 PMCID: PMC8620221 DOI: 10.3390/insects12111023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/05/2021] [Accepted: 11/11/2021] [Indexed: 11/21/2022]
Abstract
Simple Summary The armored scale known as cycad aulacaspis scale invaded Guam in 2003 and began killing individuals of the host tree Cycas micronesica by 2005. The plant mortality dynamics of this case study have been reported in detail. However, the influence of this invasion on reproductive behaviors of the host tree has not been reported. We took a look at how the male cones of this gymnosperm tree were influenced by the invasion over many years. As expected, male cones decreased substantially in size after the invasion, but then began recovering shortly thereafter. As of 2021, the cones remain only 57% as large as the pre-invasion cones. The mutualist pollinator relies on these cones as brood sites, and the ability of male cones to produce offspring of the mutualist pollinator was similarly reduced by the invasion. Conservationists need new knowledge such as this to inform species recovery efforts. Abstract Aulacaspis yasumatsui Takagi invaded Guam in 2003, and the influence on survival and demography of the host Cycas micronesica K.D. Hill population has been well-studied. To more fully understand how A. yasumatsui has threatened the host cycad species, we determined the microstrobilus size and number of pollinators per microstrobilus from 2001 to 2021. The microstrobilus height and diameter were measured directly, and the volume was calculated. Microstrobili were 58 cm in height, 13 cm in diameter, and 4740 cm3 in volume prior to direct A. yasumatsui infestations. Microstrobili decreased in size immediately after direct infestations by A. yasumatsui, and then began to slowly increase in size until 2021. For example, the volume was 24% of pre-invasion volume in 2007, and was 57% of pre-invasion volume in 2021. Microstrobili were harvested; then, the number of pollinator pupae were counted after an incubation period. Pollinator pupae counts per microstrobilus declined to 66% of pre-invasion levels by 2007 and have remained similarly constrained through 2021. Our results revealed that A. yasumatsui damage to the host C. micronesica population is not limited to attrition of the extant plant population, but also includes a loss in male reproductive effort and the risk of coextinction of the insular pollinator.
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Kim H, Kim S, Kim S, Lee Y, Lee HS, Lee SJ, Choi DS, Jeon J, Lee JH. Population Genetics for Inferring Introduction Sources of the Oriental Fruit Fly, Bactrocera dorsalis: A Test for Quarantine Use in Korea. INSECTS 2021; 12:851. [PMID: 34680620 PMCID: PMC8541597 DOI: 10.3390/insects12100851] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 11/16/2022]
Abstract
To infer the introduction sources of the oriental fruit fly, Bactrocera dorsalis, we used a mitochondrial marker to reconstruct the haplotype network and 15 microsatellite loci to reveal genetic structure and relationships between the geographically or temporally different collections from Asia. We performed Approximate Bayesian computations to infer a global origin and a source of the quarantine collections found in Korea. As a result, the 40 populations were divided into three groups, of which genetic similarity is not related to the geographic vicinity. Korean samples had a similar genetic structure to Taiwan and Thailand ones. Our results suggest that the place of origin of the B. dorsalis specimens found in Korea's border quarantine is likely to be Taiwan or Thailand. As the global origin of B. dorsalis, we estimated that Taiwan and Thailand were most likely the global origins of Southeast Asian populations by testing hypothetical scenarios by the approximate Bayesian computation analyses. Our results will allow easier identification of the source region of the forthcoming invasion of quarantined B. dorsalis specimens.
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Affiliation(s)
- Hyojoong Kim
- Animal Systematics Laboratory, Department of Biology, Kunsan National University, Gunsan 54150, Jeonbuk, Korea; (S.K.); (S.K.)
| | - Sohee Kim
- Animal Systematics Laboratory, Department of Biology, Kunsan National University, Gunsan 54150, Jeonbuk, Korea; (S.K.); (S.K.)
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
| | - Sangjin Kim
- Animal Systematics Laboratory, Department of Biology, Kunsan National University, Gunsan 54150, Jeonbuk, Korea; (S.K.); (S.K.)
| | - Yerim Lee
- Animal Systematics Laboratory, Department of Biology, Kunsan National University, Gunsan 54150, Jeonbuk, Korea; (S.K.); (S.K.)
| | - Heung-Sik Lee
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
| | - Seong-Jin Lee
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
| | - Deuk-Soo Choi
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
| | - Jaeyong Jeon
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
| | - Jong-Ho Lee
- Animal & Plant Quarantine Agency, Gimcheon 39660, Gyeongbuk, Korea; (S.-J.L.); (D.-S.C.); (J.J.); (J.-H.L.)
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Abstract
The literature covering the biology, invasion chronology, host plant responses, and control efforts of the armored scale Aulacaspis yasumatsui Takagi (Hempitera: Diaspididae) is reviewed. The small size of this cycad pest and complex surface morphology of the host cycad organs combine to make visual detection of every cryptic infestation difficult or impossible to achieve. The international movement of Cycas revoluta Thunb. nursery plants and the presence of C. revoluta nursery industries in so many countries have enabled this pest to wreak havoc on the international cycad horticulture trade over the last 25 years. The short pre-oviposition period and considerable female fecundity lead to rapid population expansion on the plants initially infested in newly invaded regions. A depletion of non-structural carbohydrates accompanies long-term infestations and precedes plant death. Enemy escape within the invasive range allows the scale population growth to remain unchecked until anthropogenic efforts establish non-native biological control.
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Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions. INSECTS 2020; 11:insects11120888. [PMID: 33339374 PMCID: PMC7767224 DOI: 10.3390/insects11120888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 11/17/2022]
Abstract
Simple Summary Effective conservation of endangered plant species requires identifying their greatest threats to formulate management protocols. Invasive species are a result of global change and are a major threat to biodiversity. We used the island cycad Cycas micronesica K.D. Hill as a model that represents the global issues of conservation science and invasion biology. In Guam, several non-native insect invasions began in 2003 and have combined to threaten the island population of this cycad species. In this article, we summarize the history of reported invasions and the reported non-native insect herbivores that have recently increased the threat status. We also discuss the interactions among herbivores that threaten the sustainability of C. micronesica on the island of Guam. Abstract Invasions of non-native species can threaten native biodiversity, and island ecosystems are ideal for studying these phenomena. In this article, first, we report on the invasive species that combine to threaten the island cycad Cycas micronesica by reviewing the history of previously reported invasions and providing an update of recent invasions. Then, we prioritize the threat status of each herbivore and the interactions among them. Plant damage was initiated in 2003─2005 by the non-native Aulacaspis yasumatsui Takagi armored scale, Erechthias sp. Meyrick leaf miner, and Luthrodes pandava Horsfield butterfly, which elicited unprecedented irruptions of the native Acalolepta marianarum Aurivillius stem borer and increased herbivory by feral pigs (Sus scrofa L.). The combined impact of these five consumers represents the greatest sustained threat to the cycad tree species. Mitigation of the damage caused by phytophagous non-native species is urgently needed to conserve this unique gymnosperm tree.
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Marler TE, Griffith MP, Krishnapillai MV. Height increment of Cycas micronesica informs conservation decisions. PLANT SIGNALING & BEHAVIOR 2020; 15:1830237. [PMID: 33073692 PMCID: PMC7671096 DOI: 10.1080/15592324.2020.1830237] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Growth dynamics of pachycaulous stems of arborescent cycad plants are not well understood, and most observations have been made in cultivated garden plants. We studied Cycas micronesica plants in Guam, Tinian, and Yap to understand the influences of geography, plant size, sex, and herbivory on stem growth. We also determined the changes in demography of Guam's population after 15 years of damage by non-native insect herbivores. The height increment (HI) was similar for plants within the height range from 100 cm to more than 600 cm, so the relative growth rate declined with height. Female tree HI was 68% of male tree HI, and Yap tree HI was 87% of Guam tree HI. Chronic herbivory by non-native insect herbivores caused a mean 44% decline in HI. Plants in managed gardens grew more rapidly than plants in a wild habitat. The HI was used to estimate that Guam has experienced a complete loss of ≈70 y of demographic depth resulting from the selective mortality of small plants since 2005. When future conservation interventions successfully mitigate the ubiquitous biological threats, our HI may be useful for empirically quantifying recovery of plant health.
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Affiliation(s)
- Thomas E. Marler
- Western Pacific Tropical Research Center, University of Guam, Mangilao, Guam, USA
- CONTACT Thomas E. Marler Western Pacific Tropical Research Center, University of Guam, Mangilao, Guam96923, USA
| | | | - Murukesan V. Krishnapillai
- Cooperative Research and Extension, College of Micronesia-FSM, Yap Campus, Yap, Federated States of Micronesia
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Abstract
The number of branches in male and female plants of Cycas micronesica K.D. Hill, Cycas edentata de Laub., Cycas wadei Merr., and Zamia encephalartoides D.W. Stev. were counted in Guam, Philippines, and Colombia, to confirm earlier reports that female plants develop fewer branches than males. Cycas plants produce determinate male strobili and indeterminate female strobili, but Zamia plants produce determinate strobili for both sexes. More than 80% of the female trees for each of the Cycas species were unbranched with a single stem, but more than 80% of the male trees exhibited two or more branches. The mean number of branches on male plants was more than double that of female plants. The number of branches of the Zamia male plants was almost triple that of female plants. Moreover, the Zamia plants produced 2.8-fold greater numbers of branches than the mean of the Cycas plants. Most of Guam’s unsexed C. micronesica trees in 2004 were unbranched, but after 15 years of damage from non-native insect herbivores, most of the remaining live trees in 2020 contained three or more branches. The results confirm that male Cycas and Zamia plants produce more branches than female plants and suggest cycad species with determinate female strobili produce more branches on female plants than species with indeterminate female strobili. Our results indicate that the years of plant mortality on Guam due to non-native insect herbivores have selectively killed more female C. micronesica trees. Horticulture and conservation decisions may be improved with this sexual dimorphism knowledge.
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Longitude, Forest Fragmentation, and Plant Size Influence Cycas micronesica Mortality Following Island Insect Invasions. DIVERSITY 2020. [DOI: 10.3390/d12050194] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Island invasions may cause severe changes in biodiversity, but the factors that influence these changes are not well understood. We established 120 plots in Cycas micronesica habitats throughout Guam in 2005 following the invasion of the armored scale Aulacaspis yasumatsui, then observed plant mortality through 2020. We used transects in Yap as benchmarks, as the Yap C. micronesica population is not threatened. The initial Guam plots contained about 1600 seedlings, 1160 juveniles, and 1240 mature plants per ha. Seedling mortality was 100% by 2006, juvenile mortality was 100% by 2014, and the 2020 census revealed 96% mortality of the plant population. Localities in western Guam and isolated forest fragments exhibited the greatest mortality, with 100% extirpation from two fragmented western localities. The juvenile and mature trees in Yap were unchanged from 2010 to 2018, but the seedling count was heterogeneous among the years. Constrained recruitment from seedlings to juveniles explained these dynamics. Yap transects contained about 6120 seedlings, 3400 juveniles, and 1250 mature plants per ha. Biological control of the invasive insects remains the acute conservation action needed for the Guam population. Lessons learned may be useful in other regions where invasions of non-native pests threaten biodiversity.
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Marler TE. Tree conservation can be constrained by agents from conservation permitting and funding agencies. Commun Integr Biol 2019; 12:133-143. [PMID: 31528243 PMCID: PMC6735646 DOI: 10.1080/19420889.2019.1654348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 08/06/2019] [Indexed: 11/15/2022] Open
Abstract
Recent conservation actions for Serianthes nelsonii Merr. and Cycas micronesica K.D. Hill in the Mariana Islands have illuminated some negative consequences associated with ill-informed agents representing permitting and funding agencies. Several cases from the islands of Guam and Tinian are discussed as ineffective conservation examples, and these are countered with two examples of successful conservation approaches. When biologists that act as points of contact for federal permitting and funding agencies do not possess education, knowledge, and experience that is germane to federally listed species, sound science may be marginalized from the conservation agenda. When rapid turnover of federal conservation agents introduces dysfunction, discontinuities in collaborations may thwart success. When lapses in conservation contracts are allowed, short-term extemporary contracting approaches are utilized, and conservation practitioners that lack the ability to include an experimental approach to conservation actions are employed, the co-production of new knowledge to enable decision support tools for future decision-makers may be hindered.
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Affiliation(s)
- Thomas E. Marler
- College of Natural and Applied Sciences, University of Guam, Mangilao, Guam, USA
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Abstract
Conservation agencies charged with care of threatened plant species should be governed by the concepts that conservation actions should do no harm. Adaptive management research progresses in imperfect situations due to incomplete knowledge. Interpreting new experimental or observational evidence for inclusion in conservation plans should first consider the big picture by identifying collateral quandaries before scaling up the approach to large-scale implementation. We discuss a case study of Cycas micronesica conservation activities on the island of Guam. The use of large stem cuttings has been shown to be a viable approach for rescuing trees from planned construction sites. However, this artificial means of producing transplants exhibits shortcomings, some of which may add new threats to the existing plant population. Moreover, devoting funds for use of the new technique in tree rescue projects does not address the primary threats that have led to listing under the United States Endangered Species Act (ESA). Transplanted trees will likely succumb to those ubiquitous threats shortly after the completion of a successful rescue project. Alternatively, investing conservation funds into mitigation of the primary threats could lead to removal of the species from the ESA.
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Affiliation(s)
- Thomas E Marler
- Western Pacific Tropical Research Center, University of Guam, UOG Station, Mangilao, Guam, USA
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