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Temporal variation in climatic factors influences phenotypic diversity of Trochulus land snails.

ABSTRACT: Organisms with limited dispersal capabilities should show phenotypic plasticity in situ to keep pace with environmental changes. Therefore, to study the influence of environmental variation on the phenotypic diversity, we chose land snails, Trochulus hispidus and T. sericeus, characterized by high population variability. We performed long-term field studies as well as laboratory and common garden experiments, which revealed that temporal environmental changes generate visible variation in shell size and shape of these snails. Many shell measurements of T. hispidus varied significantly with temperature and humidity in individual years. According to this, the first generation of T. hispidus, bred in controlled laboratory conditions, became significantly different in higher spire and narrower umbilicus from its wild parents. Interestingly, offspring produced by this generation and transplanted to wild conditions returned to the 'wild' flat and wide-umbilicated shell shape. Moreover, initially different species T. hispidus and T. sericeus transferred into common environment conditions revealed rapid and convergent shell modifications within one generation. Such morphological flexibility and high genetic variation can be evolutionarily favored, when the environment is heterogeneous in time. The impact of climate change on the shell morphometry can lead to incorrect taxonomic classification or delimitation of artificial taxa in land snails. These findings have also important implications in the context of changing climate and environment.

SUBMITTER: Prockow M

PROVIDER: S-EPMC9296580 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundIn island archipelagos, where islands have experienced repeated periods of fragmentation and connection through cyclic changes in sea level, complex among-island distributions might reflect historical distributional changes or local evolution. We test the relative importance of these mechanisms in an endemic radiation of Rhagada land snails in the Dampier Archipelago, a continental archipelago off the coast of Western Australia, where ten morphospecies have complex, overlapping distributions.ResultsWe obtained partial mtDNA sequence (COI) for 1015 snails collected from 213 locations across 30 Islands, and used Bayesian phylogenetic analysis and Analysis of Molecular Variance (AMOVA) to determine whether geography or the morphological taxonomy best explains the pattern of molecular evolution. Rather than forming distinct monophyletic groups, as would be expected if they had single, independent origins, all of the widely distributed morphospecies were polyphyletic, distributed among several well-supported clades, each of which included several morphospecies. Each mitochondrial clade had a clear, cohesive geographic distribution, together forming a series of parapatric replacements separated by narrow contact zones. AMOVA revealed further incongruence between mtDNA diversity and morphological variation within clades, as the taxonomic hypothesis always explained a low or non-significant proportion of the molecular variation. In contrast, the pattern of mtDNA evolution closely reflected contemporary and historical marine barriers.ConclusionsDespite opportunities for distributional changes during periods when the islands were connected, there is no evidence that dispersal has contributed to the geographic variation of shell form at the broad scale. Based on an estimate of dispersal made previously for Rhagada, we conclude that the periods of connection have been too short in duration to allow for extensive overland dispersal or deep mitochondrial introgression. The result is a sharp and resilient phylogeographic pattern. The distribution of morphotypes among clades and distant islands is explained most simply by their parallel evolution.

Project description:BACKGROUND:Rabies is a significant public health problem in China. Previous spatial epidemiological studies have helped understand the epidemiology of animal and human rabies in China. However, quantification of effects derived from relevant factors was insufficient and complex spatial interactions were not well articulated, which may lead to non-negligible bias. In this study, we aimed to quantify the role of socio-economic and climate factors in the spatial distribution of human rabies to support decision making pertaining to rabies control in China. METHODS:We conducted a multivariate analysis of human rabies in China with explicit consideration for spatial heterogeneity and spatial dependence effects. The panel of 20,368 cases reported between 2005 and 2013 and their socio-economic and climate factors was implemented in regression models. Several significant covariates were extracted, including the longitude, the average temperature, the distance to county center, the distance to the road network and the distance to the nearest rabies case. The GMM was adopted to provide unbiased estimation with respect to heterogeneity and spatial autocorrelation. RESULTS:The analysis explained the inferred relationships between the counts of cases aggregated to 271 spatially-defined cells and the explanatory variables. The results suggested that temperature, longitude, the distance to county centers and the distance to the road network are positively associated with the local incidence of human rabies while the distance to newly occurred rabies cases has a negative correlation. With heterogeneity and spatial autocorrelation taken into consideration, the estimation of regression models performed better. CONCLUSIONS:It was found that climatic and socioeconomic factors have significant influence on the spread of human rabies in China as they continuously affect the living environments of humans and animals, which critically impacts on how timely local citizens can gain access to post-exposure prophylactic services. Moreover, through comparisons between traditional regression models and the aggregation model that allows for heterogeneity and spatial effects, we demonstrated the validity and advantage of the aggregation model. It outperformed the existing models and decreased the estimation bias brought by omission of the spatial heterogeneity and spatial dependence effects. Statistical results are readily translated into public health policy takeaways.

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Temporal variation in climatic factors influences phenotypic diversity of Trochulus land snails.

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