Biology subjects

Teske, P.

Publications and source records attributed to Teske, P..

5 recordsLinked to original sources

bioRxiv2023

Connecting the dots: applying multispecies connectivity in marine park networkplanning

Marine ecosystems are highly dynamic, and their connectivity is affected by a complex range of biological, spatial, and oceanographic factors. Incorporating connectivity as a factor in the planning and management of marine protected areas (MPAs) is important yet challenging. Here, we used intraspecific genetic and genomic data for five marine species with varying life histories to characterise connectivity across a recently established South Australian MPA network. We generated connectivity networks, estimated cross-species concordance of connectivity patterns, and tested the impact of key spatial and oceanographic factors on each species. Connectivity patterns varied markedly among species, but were most correlated among those with similar dispersal strategies. Ordination analyses revealed significant associations with both waterway distances and oceanographic advection models. Notably, waterway distances provided better predictive power in all-species combined analyses. We extended the practical relevance of our findings by employing spatial prioritisation with Marxan, using node values derived from both genetic and geographic connectivity networks. This allowed the identification of several priority areas for conservation, and substantiated the initial decision to employ spatial distance as a proxy for biological connectivity for the design of the South Australian marine park network. Our study establishes a baseline for connectivity monitoring in South Australian MPAs, and provides guidelines for adapting this framework to other protected networks with intraspecies genetic data.

ecology↗

bioRxiv2021

Dietary specialisation in a Critically Endangered pipefish revealed by faecal eDNA metabarcoding

Understanding the dietary preferences of endangered species can be useful in implementing conservation strategies, including habitat restoration, translocation, and captive breeding. Environmental DNA (eDNA) from feces provides a non-invasive method for analyzing animal diets. Currently, metabarcoding, a PCR-based method, is the method of choice for analyzing such data. However, this method has limitations, specifically PCR bias, which can result in the overestimation of the importance of certain taxa and the failure to detect other taxa because they do not amplify. The present study compared metabarcoding with metagenomics, a marker-free method, to assess the diversity of prey items in the feces of a critically endangered South African estuarine pipefish, Syngnathus watermeyeri, and its widely distributed congener (S. temminckii) to investigate the potential dietary competition. Our results showed a distinct difference between the diets of S. watermeyeri and S. temminckii, with the former mainly consuming calanoid copepods and the latter preferring caridean shrimp. Metagenomics produced more species identifications than metabarcoding; however, most of the species identified are not present in South Africa. The identifications made by both methods mostly belonged to the same families, but some prey items were identified only by either method. Both methods would benefit from a complete reference database of South African estuarine macroinvertebrates.

ecology↗

bioRxiv2020

Genomic divergence and differential gene expression between crustacean ecotypes across a marine thermal gradient

Environmental gradients between marine biogeographical provinces separate distinct faunal communities; in the absence of absolute dispersal barriers numerous species nonetheless occur on either side of such boundaries. While the regional populations of such widespread species tend to be morphologically indistinguishable from each other, genetic evidence suggests that they represent unique ecotypes, and likely even cryptic species, that may be uniquely adapted to their local environment. Here, we explored genomic divergence in four sympatric southern African decapod crustaceans whose ranges span the boundary between the cool-temperate west coast (south-eastern Atlantic) and the warm-temperate south coast (south-western Indian Ocean) near the southern tip of the African continent. Using genome-wide data, we found that all four species comprise distinct west- and south coast ecotypes, with molecular dating suggesting divergence during the Pleistocene. Using transcriptomic data from one of the decapod crustaceans, we further found a clear difference in gene expression profiles between the west- and south coast ecotypes. This was particularly clear in the individual from the south coast, which experienced a transcriptomic shock at low temperatures that are more typical of the west coast and may explain their absence from that coastline. Our results shed new light on the processes involved in driving genomic divergence and incipient speciation.

genomics↗

bioRxiv2020

Purifying selection can reduce intraspecific mitochondrial gene variation to that of slowly-evolving nuclear rRNA

Mitochondrial DNA (mtDNA) has long been used to date the divergence between species, and to explore the time when species effective population sizes changed. The idea that mitochondrial DNA is useful for molecular dating rests on the premise that its evolution is neutral. This premise was questionable to begin with, and even though it has long been challenged, the evidence against clock-like evolution of mtDNA is usually ignored. Here, we present a particularly clear and simple example to illustrate the implications of violations of the assumption of selective neutrality. DNA sequences were generated for the mtDNA COI gene and the nuclear 28S rRNA of two closely related and widely distributed rocky shore snails whose geographical ranges are defined by different thermal preferences. To our knowledge, this is the first study to use nuclear rRNA sequence for studying species-level genealogies instead of phylogenetics, presumably because this marker is considered to be uninformative at this taxonomic level. Even though the COI gene evolves at least an order of magnitude faster, which was reflected in high inter-specific divergence, intraspecific genetic variation was similar for both markers. As a result, estimates of population expansion times based on mismatch distributions were completely different for the two markers. Assuming that 28S evolves effectively clock-like, these findings likely illustrate variation-reducing purifying selection in mtDNA at the species level, and an elevated divergence rate caused by divergent selection between the two species. Although these two selective forces together make mtDNA suitable as a DNA barcoding marker because they create a barcoding gap, estimates of demographic change can be expected to be highly unreliable. Our study contributes to the growing evidence that the utility of mtDNA beyond DNA barcoding is limited.

genetics↗

bioRxiv2018

Thermal selection drives biodiversity origination across the Atlantic/Indian Ocean boundary

Intraspecific genetic structure in widely distributed marine species often mirrors the boundaries between temperature-defined bioregions. This suggests that the same thermal gradients that maintain distinct species assemblages also drive the evolution of new biodiversity. Ecological speciation scenarios are often invoked to explain such patterns, but the fact that adaptation is usually only identified when phylogenetic splits are already evident makes it impossible to rule out the alternative scenario of allopatric speciation with subsequent adaptation. We integrated large-scale genomic and environmental datasets along one of the worlds best defined marine thermal gradients (the South African coastline) to test the hypothesis that incipient speciation in the sea is due to divergence linked to the thermal environment. We identified temperature-associated gene regions in a coastal fish species that is spatially homogeneous throughout several temperature-defined biogeographical regions on the basis of selectively neutral markers. Based on these gene regions, the species is divided into geographically distinct regional populations. Importantly, the ranges of these populations are delimited by the same ecological boundaries that define distinct infraspecific genetic lineages in co-distributed marine the species, and biogeographical disjunctions in species assemblages. Our results indicate that ecologically-mediated selection represents an early stage of marine speciation in coastal regions that lack physical dispersal barriers.

evolutionary biology↗