A basic challenge in evolutionary biology is to establish links between ecology and evolution of species. One important link is the habitat template. It has been hypothesized, that the spatial and temporal settings of a habitat strongly influence the evolution of species dispersal propensity. Here, we evaluate the importance of the habitat type on genetic population differentiation of species using freshwater habitats as a model system. Freshwater habitats are either lentic (standing) or lotic (running). On average, lotic habitats are more stable and predictable over space and time than lentic habitats. Therefore, lentic habitats should favour the evolution of higher dispersal propensity which ensures population survival of lentic species. To test for such a relationship, we used extensive data on species' genetic population differentiation of lentic and lotic freshwater invertebrates retrieved from published allozyme studies. Overall, we analysed more than 150 species from all over the world. Controlling for several experimental, biological and geographical confounding effects, we always found that lentic invertebrates exhibit, on average, lower genetic population differentiation than lotic species. This pattern was consistent across insects, crustaceans and molluscs. Our results imply fundamental differences in genetic population differentiation among species adapted to either lentic or lotic habitats. We propose that such differences should occur in a number of other habitat types that differ in spatio-temporal stability. Furthermore, our results highlight the important role of lotic habitats as reservoirs for evolutionary processes and the potential for rapid speciation.
The larvae of scarab beetles are model organisms for studying the role of physicochemical gut conditions and intestinal microbiota in symbiotic digestion, particularly of humus. Here, we address the question of whether the enlarged hindgut paunch of Pachnoda ephippiata and Pachnoda marginata, two closely related, but allopatric species, harbors a specific bacterial microbiota. Terminal restriction length fragment polymorphism (T-RFLP) analysis revealed that in both species, the bacterial hindgut community differs strongly from that in the midgut, food soil, and fecal pellets. High intra- and interspecific similarities between the T-RFLP profiles of different larvae indicate the presence of a hindgut-specific microbiota. Nevertheless, we found a clear separation of the two species. A 16S rRNA gene clone library from the hindgut of P. ephippiata identified the major phylogenetic groups as members of the Clostridia, Betaproteobacteria, and Bacteroidetes, followed by Bacillales and Deltaproteobacteria. A comparison with a previously obtained clone library of the same species corroborates both the similarities and the intraspecific variance of the hindgut microbiota.
In the African and Asian tropics, termites of the subfamily Macrotermitinae play a major role in the decomposition of dead plant material. Their ecological success lies in the obligate mutualism of the termites with fungi of the genus Termitomyces. Before the advent of molecular studies, the interaction with these fungi was poorly understood. Here, we combined available ITS sequence data from West, Central, and South Africa with data of 39 new samples from East Africa to achieve the most comprehensive view of the diversity and host specificity of Termitomyces symbionts across Africa to date. A high amount of sequence divergence in the ITS sequences was found; 11 different Termitomyces lineages in East Africa and[30 lineages across Africa were identified, and the expected diversity is estimated to be about 41 lineages. The fungal lineages belong to four major clades, each almost exclusively associated with one termite host genus. Analysis of molecular variance revealed that 40% of the ITS sequence variation occurred between host genera, indicating close co-evolution at this level. However, within host genera, fungal lineages and haplotypes were frequently shared among host species and sampling localities, except for fungal symbionts of Odontotermes. Horizontal transmission of fungal symbionts may facilitate the transfer of haplotypes and species among hosts. However, at present, we have little understanding of the maintenance of specificity at the genus level. Possible explanations range from substrate specificity of fungi to an active selection of fungi by termites.
Among the many concerns for biodiversity in the Anthropocene, recent reports of flying insect loss are particularly alarming, given their importance as pollinators, pest control agents, and as a food source. Few insect monitoring programmes cover the large spatial scales required to provide more generalizable estimates of insect responses to global change drivers. We ask how climate and surrounding habitat affect flying insect biomass using data from the first year of a new monitoring network at 84 locations across Germany comprising a spatial gradient of land cover types from protected to urban and crop areas. Flying insect biomass increased linearly with temperature across Germany. However, the effect of temperature on flying insect biomass flipped to negative in the hot months of June and July when local temperatures most exceeded long‐term averages. Land cover explained little variation in insect biomass, but biomass was lowest in forests. Grasslands, pastures, and orchards harboured the highest insect biomass. The date of peak biomass was primarily driven by surrounding land cover, with grasslands especially having earlier insect biomass phenologies. Standardised, large‐scale monitoring provides key insights into the underlying processes of insect decline and is pivotal for the development of climate‐adapted strategies to promote insect diversity. In a temperate climate region, we find that the positive effects of temperature on flying insect biomass diminish in a German summer at locations where temperatures most exceeded long‐term averages. Our results highlight the importance of local adaptation in climate change‐driven impacts on insect communities.
Aim The freshwater flatworm Crenobia alpina lives almost exclusively in headwaters of mountainous areas and is supposed to be a glacial relict. We examined genetic diversity within and between populations of C. alpina in order to determine the taxonomic status of purported subspecies and to understand large‐scale biogeographical patterns of glacial relicts. Location Central Europe. Methods We analysed mitochondrial DNA sequences and polymorphic allozyme loci of C. alpina populations across its range in central Europe. Sequences were compared using parsimony, minimum evolution and maximum likelihood. Allozymes were analysed using traditional as well as Bayesian estimates of F statistics. Results We found considerable divergence between haplotypes. For each of the two lineages occurring throughout central Europe, allozymes showed considerable differentiation between populations and a strong isolation by distance effect. Hence populations are effectively isolated even across rather small spatial scales. Main conclusions There is strong evidence that C. alpina is a complex of distinct lineages or cryptic species that date back to the late Miocene. The separation of lineages may be associated with the formation of deep valleys at the end of the Messinian Crisis.
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