Biology subjects

Measey, J.

Publications and source records attributed to Measey, J..

5 recordsLinked to original sources

bioRxiv2023

Impacts of invasive fishes on ghost frog tadpoles

Global amphibian populations are declining, and invasive fish are known to impact many threatened species. South Africa has both a biodiverse amphibian fauna and a rich history of invasive fish introductions with high establishment success. Studies have identified some preliminary evidence for negative impacts of invasive salmonids on two ghost frog species (Anura: Heleophrynidae). This study aims to investigate whether these negative impacts previously reported are reflected across a broader scale. Tadpoles of two species, Heleophryne regis and H. purcelli were sampled in the presence and absence of invasive fish at 112 sites across 26 streams in the Western Cape province of South Africa. A generalised linear mixed model showed invasive fish to have the most significant negative effect explaining tadpole abundance. Mean tadpole abundance decreases by 18 times in the presence of invasive fish. Environmental variables with significant effects on tadpole abundance include pH, oxygen saturation, temperature, stream depth and non-native riparian vegetation type. We can define an environmental niche of ghost frog tadpoles which does not differ between species. We conclude that invasive fish have significant negative impacts on ghost frog tadpole abundance, but the effect of the environment should not be overlooked in amphibian conservation planning and invasive species management decisions. This study supports the removal of invasive fish and alien vegetation to improve the conservation of ghost frogs.

ecology↗

bioRxiv2022

Population genomics of Xenopus laevis in southern Africa

Allotetraploid genomes have two distinct genomic compartments called subgenomes that are derived from separate diploid ancestral species. Many genomic characteristics such as gene function, expression, recombination, and transposable element mobility may differ significantly between subgenomes. To explore the possibility that subgenome population structure and gene flow may differ as well, we examined genetic variation in an allotetraploid frog - the African clawed frog (Xenopus laevis) - over the dynamic and varied habitat of its native range in southern Africa. Using reduced representation genome sequences from 91 samples from 12 localities, we found no strong evidence that population structure and gene flow differed substantially by subgenome. We then compared patterns of population structure in the nuclear genome to the mitochondrial genome using Sanger sequences from 455 samples from 183 localities. Our results provide further resolution to the geographic distribution of mitochondrial and nuclear diversity in this species and illustrate that population structure in both genomes corresponds roughly with variation in seasonal rainfall and with the topography of the southern Africa.

genetics↗

bioRxiv2022

Population estimation of a cryptic moss frog using acoustic spatially explicit capture recapture

Cryptic amphibians pose a problem for conservation managers as they are difficult to find to assess initial populations, and monitor changes during potentially threatening processes. The rough moss frog, Arthroleptella rugosa, is small and occurs in seepages on a single unprotected mountain in South Africas fire prone, biodiverse fynbos biome. The area is heavily impacted by invasive plants, which dry seepages and increase the frequency and intensity of fires, leading to the assessment of this species as Critically Endangered. We aimed to test the efficacy of acoustic spatially explicit capture recapture (aSCR) to estimate the entire population of calling adult A. rugosa, and assess the impacts by invasive plants. Using aSCR, our estimates suggest that the population of A. rugosa is more than five times that previously estimated using aural calling surveys on the mountain, at [~]2000 individuals. This despite an intense fire over the entire area three years earlier that reduced the calling population to a few tens of individuals. Our vegetation surveys suggest that the ongoing removal of invasive plants from the mountain is successful in areas occupied by A. rugosa, but that adjacent areas invaded by pines and hakea have a negative impact on calling density. The private public conservancy partnership on Klein Swartberg Mountain, is conserving this frog but will require ongoing management and monitoring to ensure conservation in the future.

ecology↗

bioRxiv2020

The gut microbiome facilitates ecological adaptation in an invasive vertebrate

Gut microbial communities regulate host physiology and health of humans and laboratory animals. The functional significance of these collective bacterial genomes (i.e. the microbiome) to the adaptive potential of wildlife hosts is still unknown. Studies demonstrating convincing examples of microbial flexibility to environmental change so far lack the experimental approaches to demonstrate the effect on host physiology. Invasive species provide natural experiments to tease apart these host-microbe relationships. However, no studies have investigated how microbial symbionts might mediate responses of invasive hosts physiology to environmental change. In this study, we examine whether invasive gut microbiomes have significantly diverged in their ability to respond to novel environmental change (i.e. a dietary challenge) compared to native gut microbiomes by performing reciprocal faecal microbial transplant (FMT) experiments in native and invasive guttural toad (Sclerophrys gutturalis) populations. Subsequently, we determine how the microbiome regulates host physiological changes in response to a dietary challenge. We show that invasive gut microbiomes exhibit higher microbial compositional and predicted functional flexibility to novel dietary change, compared to native gut microbiomes. This increased microbial flexibility is coupled with significant flexibility in energy harvesting. Furthermore, our results indicate that overall invasive gut microbiomes significantly upregulate energy harvesting and physiological performance of hosts, compared to native microbiomes. Our study is the first identifying gut microbiota as the sole factor contributing to the adaptive physiology of a vertebrate using a unique study design. These findings provide novel insights into the key role of gut microbial symbionts in increasing the invasive potential of its vertebrate host.

ecology↗

bioRxiv2019

TAXONOMIC BIAS AND TRAITS OF THE GLOBAL AMPHIBIAN PET-TRADE

The pet-trade is recognized as the major pathway for amphibian introductions worldwide, yet our understanding of the trade is limited. In this study, we systematically assess amphibian species in the pet-trade, i) characterising taxonomic bias and ii) evaluating species-traits as predictors of traded species and trade volume. We collated a global list of 443 traded amphibians and a regional dataset on trade volume. Species-traits (body size, native range size, clutch size, and breeding type) and conservation status, were considered as predictors of traded species and volume. We found a strong bias for certain Families, along with a preference for large-bodied and widely distributed species with a larval phase, in the pet-trade. However, species-traits performed poorly in predicting trade volume of pet amphibians in the USA. The identified species-traits and taxonomic bias of the trade is used to predict species likely to be traded as pets in the future.

ecology↗