Urban environment decreases pollinator availability, fertility, and prolongs anthesis in the field bindweed (Convolvulus arvensis Linnaeus, 1753)

Urbanization alters the natural environment, with broad negative impacts on living organisms. Urbanization can also disrupt plant-pollinator networks by reducing the abundance and diversity of invertebrates. Firstly, I investigated whether the field bindweed (Convolvulus arvensis) is an obligatory entomophilous plant because previous reports were ambiguous. Secondly, I investigated how the obligatory entomophilous plant, field bindweed, responds to urbanization by comparing the flowering duration (anthesis) and the reproductive success of field bindweeds in urban and rural populations. Unlike cross-pollinated flowers and controls, flowers experimentally prevented from pollination and self-pollinated flowers did not produce seeds, suggesting that the field bindweed is self-incompatible and obligatory entomophilous. The abundance of urban pollinators was 5-6 times lower than the abundance of rural pollinators, and flies (Diptera), beetles (Coleoptera) and moths (Lepidoptera) were significantly more negatively influenced by the urban environment than hymenopterans (Hymenoptera). Urban plants showed significantly longer anthesis duration and lower reproductive success than rural plants. Illuminance and low pollinator abundance were negatively associated with the duration of the anthesis, but relative humidity did not affect the anthesis. Prolonged duration of the anthesis may be an adaptation to pollinator scarcity because more prolonged flowering increases the likelihood of pollination. Future research should unravel whether the longer anthesis of urban flowers is determined by behavioral plasticity or by the evolutionary selection of plants with a genetically determined longer anthesis.

Enhanced plasticity and reproductive fitness of floral and seed traits facilitate non-native species spread in mountain ecosystems

Floral and seed traits, their relationships, and responses to abiotic constraints are considered the key determinants of the invasion success of non-native plant species. However, studies evaluating the pattern of floral and seed traits of non-native species in mountain ecosystems are lacking. In this study, we determined (a) whether the floral and seed traits of native and non-native species show similarity or dissimilarity across elevations in mountains, and (b) whether the non-native species follow different allometric patterns compared with native species. Functional variations between native and non-native species were assessed through floral and seed traits: flower count, flower display area, flower mass, specific flower area, seed count, and seed mass across an elevational gradient. Permanent plots (20 × 20 m) were laid at each 100 m elevation rise from 2000 to 4000 m a.s.l. for sampling of herbaceous plant species. The mean values of floral and seed traits such as flower display area, specific flower area, and seed count were significantly higher for non-native species compared to native species. A significant difference in trait values (flower display area, flower mass, seed count, and seed mass) between non-native species and native species was observed along the elevational gradient, except for flower count and specific flower area. The bivariate relationship revealed non-native species to exhibit a stronger relationship between flower display area ∼ flower mass, and flower display area ∼ seed mass traits than the native species. Non-native species showed enhanced reproductive ability under varying environmental conditions along an elevational gradient in mountain ecosystems. Greater flower display area and seed mass at lower elevations and a stronger overall trait-trait relationship among non-native species implied resource investment in pollinator visualization, flower mass, and seed quality over seed quantity. The study concludes that enhanced plasticity and reproductive fitness of floral and seed traits would consequently aid non-native species to adapt, become invasive, and displace native species in mountain ecosystems if the climatic barriers acting on non-native species are reduced with climate change.

The role of intra-guild indirect interactions in assembling plant-pollinator networks

Understanding the assembly of plant-pollinator communities has become critical to their conservation given the rise of species invasions, extirpations, and species' range shifts. Over the course of assembly, colonizer establishment produces core interaction patterns, called motifs, which shape the trajectory of assembling network structure. Dynamic assembly models can advance our understanding of this process by linking the transient dynamics of colonizer establishment to long-term network development. In this study, we investigate the role of intra-guild indirect interactions and adaptive foraging in shaping the structure of assembling plant-pollinator networks by developing: 1) an assembly model that includes population dynamics and adaptive foraging, and 2) a motif analysis tracking the intra-guild indirect interactions of colonizing species throughout their establishment. We find that while colonizers leverage indirect competition for shared mutualistic resources to establish, adaptive foraging maintains the persistence of inferior competitors. This produces core motifs in which specialist and generalist species coexist on shared mutualistic resources which leads to the emergence of nested networks. Further, the persistence of specialists develops richer and less connected networks which is consistent with empirical data. Our work contributes new understanding and methods to study the effects of species' intra-guild indirect interactions on community assembly.

Leaf morpho-physiological comparison between native and non-native plant species in a Mediterranean island

Islands tend to be more prone to plant invasions than mainland regions, with the Mediterranean ones not being an exception. So far, a large number of studies on comparing leaf morphological and physiological traits between native and non-native plants in Mediterranean environments have been performed, although none of them on Mediterranean islands. To fill this gap, this study focuses on 14 plant species grown in a controlled growth chamber in the absence of stress. The goal was (1) to differentiate leaf morpho-physiological traits between native and non-native plants on a Mediterranean island and (2) to deepen in the underlying causes of the differential photosynthetic traits displayed by non-native species. Results showed that in Mediterranean islands, non-native plant species show on average larger values of net CO2 assimilation, stomatal conductance (gm), photosynthetic nitrogen-use efficiency, among others, and lower leaf mass per area (LMA) and leaf thickness, compared to the native species. Among the assessed traits, this study reports for the first time larger gm, and lower mesophyll conductance limitation in non-native species, which seems to be linked to their lower LMA. These novel traits need to be added to the ‘leaf physiological trait invasive syndrome’. It was also found that on a Mediterranean island, native and non-native species are placed on opposite sides of the leaf economics spectrum, with non-native species being placed on the ‘‘fast-return’’ end. In conclusion, this study demonstrates that non-native species inhabiting a Mediterranean island possess distinct leaf morphological and physiological traits compared to co-occurring native species, at least during the favorable growth season, which increases the chances of a successful invasion.