Patterns and drivers of Nothobranchius killifish diversity in lowland Tanzania

Abstract

Temporary pools are seasonal wetland habitats with specifically adapted biota, including annual Nothobranchius killifishes that survive habitat desiccation as diapausing eggs encased in dry sediment. To understand the patterns in the structure of Nothobranchius assemblages and their potential in wetland conservation, we compared biodiversity components (alpha, beta, and gamma) between regions and estimated the role and sources of nestedness and turnover on their diversity. We sampled Nothobranchius assemblages from 127 pools across seven local regions in lowland Eastern Tanzania over 2 years, using dip net and seine nets. We estimated species composition and richness for each pool, and beta and gamma diversity for each region. We decomposed beta diversity into nestedness and turnover components. We tested nestedness in three main regions (Ruvu, Rufiji, and Mbezi) using the number of decreasing fills metric and compared the roles of pool area, isolation, and altitude on nestedness. A total of 15 species formed assemblages containing 1–6 species. Most Nothobranchius species were endemic to one or two adjacent regions. Regional diversity was highest in the Ruvu, Rufiji, and Mbezi regions. Nestedness was significant in Ruvu and Rufiji, with shared core ( N . melanospilus , N . eggersi , and N . janpapi ) and common ( N. ocellatus and N . annectens ) species, and distinctive rare species. Nestedness apparently resulted from selective colonization rather than selective extinction, and local species richness was negatively associated with altitude. The Nothobranchius assemblages in the Mbezi region were not nested, and had many endemic species and the highest beta diversity driven by species turnover. Overall, we found unexpected local variation in the sources of beta diversity (nestedness and turnover) within the study area. The Mbezi region contained the highest diversity and many endemic species, apparently due to repeated colonizations of the region rather than local diversification. We suggest that annual killifish can serve as a flagship taxon for small wetland conservation.

Conserved satellite DNA motif and lack of interstitial telomeric sites in highly rearranged African Nothobranchius killifish karyotypes

“…We analysed 63 individuals belonging to 15 Nothobranchius killifish species (18 populations) from four phylogenetic clades, and the out‐group species F. thierryi . The studied individuals from Nothobranchius orthonotus , Nothobranchius kuhntae , Nothobranchius pienaari , Nothobranchius rachovii , Nothobranchius eggersi , Nothobranchius rubripinnis , and Nothobranchius melanospilus were sampled from laboratory populations recently derived from wild‐caught individuals and were previously identified based on morphology and the phylogenetic analysis of mitochondrial and nuclear markers (see Bartáková et al, 2015; Bartakova & Reichard, 2023; Blažek et al, 2017; Reichard, Giannetti, et al, 2022; Reichard, Janáč, et al, 2022). The remaining species were obtained from specialists and experienced hobby breeders who keep strictly population‐specific lineages derived from original imports.…”

Conserved satellite DNA motif and lack of interstitial telomeric sites in highly rearranged AfricanNothobranchiuskillifish karyotypes

“…We analyzed 63 individuals belonging to 15 Nothobranchius killifish species (18 populations) from four phylogenetic clades, and the outgroup species Fundulosoma thierryi . The studied individuals from N. orthonotus , N. kuhntae , N. pienaari , N. rachovii , N. eggersi , N. rubripinnis and N. melanospilus were sampled from laboratory populations recently derived from wild-caught individuals and were previously identified based on morphology and the phylogenetic analysis of mitochondrial and nuclear markers (see [Bartáková et al, 2015; Blažek et al, 2017; Reichard et al, 2022a, b]). The remaining species were obtained from specialists and experienced hobby breeders who keep strictly population-specific lineages derived from original imports.…”