Behavior influences range limits and patterns of coexistence across an elevational gradient in tropical bird diversity, bioRxiv, 2019-01-24

Does competition influence patterns of coexistence between closely related taxa? Here we address this basic question in ecology by analyzing patterns of range overlap between related bird species (sister pairs) distributed along a Neotropical elevational gradient. We explicitly contrast the behavioral dimension of interspecific competition (interference competition) with similarity in resource acquisition traits (exploitative competition). We find that behavioral interactions are generally important in setting elevational range limits and preventing coexistence of closely related species. Specifically, close relatives that defend year-round territories tend to live in non-overlapping elevational distributions, while close relatives that do not defend territories tend to broadly overlap in distribution. In contrast, neither similarity in beak morphology nor evolutionary relatedness was associated with patterns of range limitation. Our main result is that interference competition can be an important driver of species ranges at the scale of entire diverse assemblages. Consequently, we suggest that behavioral dimensions of the niche should be more broadly incorporated in macroecological studies.

Flowers respond to pollinator sound within minutes by increasing nectar sugar concentration, bioRxiv, 2018-12-29

Can plants hear? That is, can they sense airborne sounds and respond to them? Here we show that Oenothera drummondii flowers, exposed to the playback sound of a flying bee or to synthetic sound-signals at similar frequencies, produced sweeter nectar within 3 minutes, potentially increasing the chances of cross pollination. We found that the flowers vibrated mechanically in response to these sounds, suggesting a plausible mechanism where the flower serves as the plant’s auditory sensory organ. Both the vibration and the nectar response were frequency-specific the flowers responded to pollinator sounds, but not to higher frequency sound. Our results document for the first time that plants can rapidly respond to pollinator sounds in an ecologically relevant way. Sensitivity of plants to pollinator sound can affect plant-pollinator interactions in a wide range of ways Plants could allocate their resources more adequately, focusing on the time of pollinator activity; pollinators would then be better rewarded per time unit; flower shape may be selected for its effect on hearing ability, and not only on signaling; and pollinators may evolve to make sounds that the flowers can hear. Finally, our results suggest that plants may be affected by other sounds as well, including antropogenic ones.

Climate or disturbance temperate forest structural change and carbon sink potential, bioRxiv, 2018-11-27

ABSTRACTAnticipating forest responses to changing climate and disturbance regimes requires understanding long-term successional processes and aggregating these local processes into global relevance. Estimates of existing forest structure and biomass are improving globally; however, vegetation models continue to show substantial spread in predictions of future land carbon uptake and the roles of forest structural change and demography are increasingly being recognized as important. To identify mechanisms that drive change in tree size, density, and carbon, we need a better understanding of forest structural trajectories and the factors that affect those trajectories. Here we reveal a coherent, cyclic pattern of structural change in temperate forests, as predicted by successional theory, and identify significant sensitivity to climatic precipitation and temperature anomalies using large datasets and empirical modeling. For example, in the eastern US above average temperature (+1°C) was associated with a 27% (−0.4±0.1 Mg C ha-1 yr-1) reduction in productivity attributed to higher rates of disease (+23%), weather disturbance (+57%), and sapling mortality. Projections of future vegetative carbon sink potential suggests biomass would be lowest on managed lands (72±2 Mg C ha-1) and highest when larger trees survive in undisturbed conditions (153±21 Mg C ha-1). Overall, the indirect effects of disturbance and mortality were considerably larger than the direct effects of climate on productivity when predicting future vegetative carbon sinks. Results provide robust comparisons for global vegetation models, and valuable projections for management and carbon mitigation efforts.

Defining trait-based microbial strategies with consequences for soil carbon cycling under climate change, bioRxiv, 2018-10-17

First detection of a highly invasive freshwater amphipod (Crangonyx floridanus) in the United Kingdom, bioRxiv, 2018-10-11

AbstractThe freshwater gammarid, Crangonyx floridanus, originates from North America but has invaded and subsequently spread rapidly throughout Japan. We provide here the first genetic and microscopic evidence that C. floridanus has now also reached the United Kingdom. We found this species in two locations separated by more than 200 km (Lake Windermere in the North of the UK and Smestow Brook, West Midlands). The current distribution of C. floridanus is currently unknown, however both sites are well connected to other river and channel systems therefore the chance of further spread is high. Genetic analyses of C. floridanus indicate that British inland waters are colonised by the same linage, which also has invaded Japan. We recommend further work to assess the distribution of this species and its impact on the local fauna and flora.

The ecological drivers of variation in global language diversity, bioRxiv, 2018-09-26

AbstractLanguage diversity is distributed unevenly over the globe. Why do some areas have so many different languages and other areas so few? Intriguingly, patterns of language diversity resemble biodiversity patterns, leading to suggestions that similar mechanisms may underlie both linguistic and biological diversification. Here we present the first global analysis of language diversity that identifies the relative importance of two key ecological mechanisms suggested to promote language diversification - isolation and ecological risk - after correcting for spatial autocorrelation and phylogenetic non-independence. We find significant effects of climate on language diversity consistent with the ecological risk hypothesis that areas of high year-round productivity lead to more languages by supporting human cultural groups with smaller distributions. Climate has a much stronger effect on language diversity than landscape features that might contribute to isolation of cultural groups, such as altitudinal variation, river density, or landscape roughness. The association between biodiversity and language diversity appears to be an incidental effect of their covariation with climate, rather than a causal link between the two. While climate and landscape provide strong explanatory signal for variation in language diversity, we identify a number of areas of high unexplained language diversity, with more languages than would be predicted from environmental features alone; notably New Guinea, the Himalayan foothills, West Africa, and Mesoamerica. Additional processes may be at play in generating higher than expected language diversity in these regions.