Dataset Information

Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves.

ABSTRACT: Caves offer selective pressures that are distinct from the surface. Organisms that have evolved to exist under these pressures typically exhibit a suite of convergent characteristics, including a loss or reduction of eyes and pigmentation. As a result, cave-obligate taxa, termed troglobionts, are no longer viable on the surface. This circumstance has led to an understanding of highly constrained dispersal capabilities, and the prediction that, in the absence of subterranean connections, extreme genetic divergence between cave populations. An effective test of this model would involve (1) common troglobionts from (2) nearby caves in a cave-dense region, (3) good sample sizes per cave, (4) multiple taxa, and (5) genome-wide characterization. With these criteria in mind, we used RAD-seq to genotype an average of ten individuals of the troglobiotic spider Nesticus barri and the troglobiotic beetle Ptomaphagus hatchi, each from four closely located caves (ranging from 3 to 13 km apart) in the cave-rich southern Cumberland Plateau of Tennessee, USA. Consistent with the hypothesis of highly restricted dispersal, we find that populations from separate caves are indeed highly genetically isolated. Our results support the idea of caves as natural laboratories for the study of parallel evolutionary processes.

SUBMITTER: Balogh A

PROVIDER: S-EPMC7568537 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves.

Balogh Andras A Ngo Lam L Zigler Kirk S KS Dixon Groves G

Scientific reports 20201016 1

Caves offer selective pressures that are distinct from the surface. Organisms that have evolved to exist under these pressures typically exhibit a suite of convergent characteristics, including a loss or reduction of eyes and pigmentation. As a result, cave-obligate taxa, termed troglobionts, are no longer viable on the surface. This circumstance has led to an understanding of highly constrained dispersal capabilities, and the prediction that, in the absence of subterranean connections, extreme ...[more]

PMID: 33067497

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Project description:BackgroundThe increasing human impact in Romanian caves raises the urgency of publishing a correct database of the strictly-adapted cave fauna. Previous attempts at indexing cave fauna and classifying caves by using their fauna opened many questions regarding the use of an incomplete list of cave species and mixed lists of troglobionts/stygobionts with troglophiles/stygophiles for ranking caves with priority for protection. It has also become obvious that there is a need to publish a list of Romanian cave species that are under threat. Cave species in Romania (and elsewhere) are endemic on small ranges, are unique and must be considered as important units for conservation. A cave must be equally protected if it has one or more rare and strictly endemic cave species. Although not exhaustive, we here provide the first checklist of Romanian troglobionts/stygobionts developed in the framework of the DARKFOOD and GROUNDWATERISK projects, coordinated by the "Emil Racovita" Institute of Speleology, Cluj-Napoca, Romania. The GIS application was used to complement the checklist of cave species with data on caves and surface environments above the caves. Until complete data on species diversity and population sizes are made available for each cave, measures of conservation can be implemented, based on the presence/absence of cave species, while classifications of caves for protection, based on the number of species, must be avoided. We also propose a list of Romanian caves with fauna that are under threat and a tentative Red List of Romanian troglobiont/stygobionts.New informationThis is the first database with identified troglobiont and stygobiont species of Romania, with a critical analysis of their distribution inside the country. A list of caves that need protection for their rare and unique species and a tentative Red List of Romanian cave fauna are also added. A total of 173 species were identified, of which 77 troglobionts and 96 stygobionts are currently registered in 366 caves. The database is divided into two parts, one part with a list of troglobionts, their revised systematic position, cave name, cave code and geographic region; and the second part with the same information on stygobionts. The database represents the contribution of many active researchers, who are the authors of this paper and of review publications of many other authors of the "Emil Racoviță" Institute of Speleology.

Project description:It is commonly accepted that species interactions such as granivory are more intense in the tropics. However, this has rarely been tested. A global dataset of post-dispersal seed removal by invertebrates and vertebrates for 79 native plant species from semi-natural and natural terrestrial habitats ranging from 55° N to 45° S, was compiled from the global literature to test the hypothesis that post-dispersal seed removal by invertebrates and vertebrates is more intense at lower latitudes. We also quantified the relationship between post-dispersal seed removal by vertebrates and by invertebrates to global climatic features including temperature, actual evapotranspiration (AET) and rainfall seasonality. Linear mixed effect models were applied to describe the relationships between seed removal and latitude, hemisphere and climatic variables controlling for the effect of seed mass. Post-dispersal seed removal by invertebrates was negatively related to latitude. In contrast, post-dispersal seed removal by vertebrates was positively but weakly related to latitude. Mean annual temperature and actual evapotranspiration were positively related to post-dispersal seed removal by invertebrates, but not to post-dispersal seed removal by vertebrates, which was only marginally negatively related to rainfall seasonality. The inclusion of seed mass improved the fit of all models, but the term for seed mass was not significant in any model. Although a good climatic model for predicting post-dispersal seed predation by vertebrates at the global level was not found, our results suggest different and opposite latitudinal patterns of post-dispersal seed removal by invertebrates vs vertebrates. This is the first time that a negative relationship between post-dispersal seed removal by invertebrates and latitude, and a positive relationship with temperature and AET have been documented at a global-scale. These results have important implications for understanding global patterns in plant-animal interactions, and the factors that shape plant reproductive ecology, and also for predicting how this plant-animal interaction might respond to climate change.

Project description:The relative importance of environment and dispersal related processes for community assembly has attracted great interest over recent decades, but few empirical studies from the marine/estuarine realm have examined the possible effects of these two types of factors in the same system. Importance of these processes was investigated in a hypothetical metacommunity of benthic invertebrates in 16 micro-tidal estuaries connected to the same open sea area. The estuaries differed in size and connectivity to the open sea and represented a salinity gradient across the estuaries. The Elements of Metacommunity Structure (EMS) approach on estuary scale was complemented with a mechanistic variance partitioning approach on sample scale to disentangle effects of factors affecting assembly of three trait groups of species with different dispersivity. A quasi-Clementsian pattern was observed for all three traits, a likely response to some latent gradient. The primary axis in the pattern was most strongly related to gradients in estuary salinity and estuary entrance width and correlation with richness indicated nestedness only in the matrix of the most dispersive trait group. In the variance partitioning approach measures of turnover and nestedness between paired samples each from different estuaries were related to environmental distance in different gradients. Distance between estuaries was unimportant suggesting importance of factors characterizing the estuaries. While the high dispersive species mainly were sorted in the salinity gradient, apparently according to their tolerance ranges towards salinity, the two less dispersive traits were additionally affected by estuary entrance width and possibly also area. The results exemplify a mechanism of community assembly in the marine realm where the niche factor salinity in conjunction with differential dispersal structure invertebrates in a metacommunity of connected estuaries, and support the idea that dispersive species are more controlled by the environment than less dispersive species.

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Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves.

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Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves.

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