Biology subjects

Schmidt, B. R.

Publications and source records attributed to Schmidt, B. R..

3 recordsLinked to original sources

bioRxiv2024

Lineage-specific trait variation generates widespread, contemporaneous coexistence and competitive exclusion dynamics in an invasive, multihost wildlife parasite

Invasive and highly virulent parasites are emerging worldwide, transported to new locations and into novel hosts by anthropogenic activities. Multiple introduction events lead to interactions amongst genetically dissimilar genotypes that can result in either competitive exclusion, coexistence, or cycling through a combination of the two. Here, we report how intra-lineage trait variation of the multihost amphibian parasite Batrachochytrium dendrobatidis drives contrasting outcomes of inter-lineage interactions on two continents, Europe and Africa. Through field surveys, competition experiments and mathematical modelling we show that interactions between the same two lineages in the two continents and in different hosts demonstrate both ends of the exclusion/coexistence continuum. Trait variation in one of the two predominating lineages, BdGPL, is responsible for these contrasting outcomes: In Europe, BdGPL is highly competitive and has constrained the distribution of the other, BdCAPE, to two locations. In Africa, BdGPL and BdCAPE can mutually invade host populations when the other lineage is already resident, potentially leading to coinfections and recombination. That these contrasting outcomes are prolonged and contemporaneous for the same two lineages shows that epidemiological models of invasive parasites need to account for trait variation both within and across lineages.

ecology↗

bioRxiv2022

Four decades of phenology in an alpine amphibian: trends, stasis and climatic drivers

O_LIStrong phenological shifts in response to changes in climatic conditions have been reported for many species, including amphibians, which are expected to breed earlier. Phenological shifts in breeding are observed in a wide number of amphibian populations, but less is known about populations living at high elevations, which are predicted to be more sensitive to climate change than lowland populations. C_LIO_LIThe goal of this study is to assess the main factors determining the timing of breeding in an alpine population of the common toad (Bufo bufo) and to describe the observed shifts in its breeding phenology. C_LIO_LIWe modelled the effect of environmental variables on the start and peak dates of the breeding season using 39 years of individual-based data. In addition, we investigated the effect of the lunar cycle, as well as the individual variation in breeding phenology. Finally, to assess the individual heterogeneity in the timing of breeding, we calculated the repeatability of the timing of arrival at the breeding site. C_LIO_LIBreeding advanced to earlier dates in the first years of the study but the trend continued only until the mid 1990s, and stabilised afterwards. Overall, toads are now breeding on average around 30 days earlier than at the start of the study period. High temperatures and low snow cover in winter and spring, as well as reduced spring precipitation were all associated with earlier breeding. Additionally, we found evidence of males arriving on average before females at the breeding site but no clear and strong effect of the lunar cycle. We only found weak evidence of among-individual variation in shifts in the breeding phenology, as well as a low repeatability of arrival timing. C_LIO_LIOur findings show that the observed changes in breeding phenology are strongly associated with the environmental conditions. These results contribute to filling a knowledge gap on the effects ssof climate change on alpine amphibian populations. Moreover, we show that changes in phenology, especially in the mountains, can be hard to predict as local microclimatic conditions do not necessarily reflect the observed global climatic trends. C_LI

ecology↗

bioRxiv2019

Slow life-history strategies are associated with negligible actuarial senescence in western Palearctic salamanders

Actuarial senescence (hereafter \"senescence\") has been viewed for a long time as an inevitable and uniform process. However, the work on senescence has mainly focused on endotherms (especially mammals) with deterministic growth and low regeneration capacity at adult stages, leading to a strong taxonomic bias in the study of aging. Recent studies have highlighted that senescence could indeed display highly variable trajectory shape that correlates with species life history traits. Slow life histories and indeterminate growth seem to be associated with weak and late senescence. Furthermore, a few studies have suggested that high regenerative abilities could make senescence negligible in several ectotherms (e.g., hydra and salamanders). However, demographic data for species that would allow testing of these hypotheses are scarce and fragmented. Here, we investigated senescence patterns in a group of salamanders (i.e. \"true salamanders\") from the Western Palearctic using capture-recapture data and Bayesian modeling. Our results showed that salamanders have slow life histories and that they experience negligible senescence. This pattern was consistent at both intra- and interspecific levels, suggesting that the absence of senescence may be a phylogenetically conserved trait. The regenerative capacities of true salamanders, and urodeles in general, likely explains why these small ectotherms have lifespans similar to that of large endotherms (e.g., ungulates, large birds) and undergo negligible senescence contrary to most amniotes including humans. Our study seriously challenges the idea that senescence is a ubiquitous phenomenon in the living world.

ecology↗