Evolutionary divergence in life history traits among populations of the Lake Malawi cichlid fishAstatotilapia calliptera

Abstract

During the early stages of adaptive radiation, populations diverge in life history traits such as egg size and growth rates, in addition to eco‐morphological and behavioral characteristics. However, there are few studies of life history divergence within ongoing adaptive radiations. Here, we studied Astatotilapia calliptera, a maternal mouthbrooding cichlid fish within the Lake Malawi haplochromine radiation. This species occupies a rich diversity of habitats, including the main body of Lake Malawi, as well as peripheral rivers and shallow lakes. We used common garden experiments to test for life history divergence among populations, focussing on clutch size, duration of incubation, egg mass, offspring size, and growth rates. In a first experiment, we found significant differences among populations in average clutch size and egg mass, and larger clutches were associated with smaller eggs. In a second experiment, we found significant differences among populations in brood size, duration of incubation, juvenile length when released, and growth rates. Larger broods were associated with smaller juveniles when released and shorter incubation times. Although juvenile growth rates differed between populations, these were not strongly related to initial size on release. Overall, differences in life history characters among populations were not predicted by major habitat classifications (Lake Malawi or peripheral habitats) or population genetic divergence (microsatellite‐based F ST). We suggest that the observed patterns are consistent with local selective forces driving the observed patterns of trait divergence. The results provide strong evidence of evolutionary divergence and covariance of life history traits among populations within a radiating cichlid species, highlighting opportunities for further work to identify the processes driving the observed divergence.

oca2targeting using CRISPR/Cas9 in the Malawi cichlidAstatotilapia calliptera

“…Nonetheless, we observed transmission of mutations to the next generation in both cases. A. calliptera species reach maturity on average at 8 months at which point they usually lay on average ~20 eggs, with clutch size increasing with age and size (Parsons et al, 2017). Despite low survival and low clutch sizes at young ages, germline transmission is high and as such it is possible to establish a breeding population of stable mutant A. calliptera within 16 months.…”

“…Here, we report the application of CRISPR/Cas9 to generate coding and non-coding sequence mutants in the cichlid Astatotilapia calliptera, a maternal mouthbrooder cichlid fish that is part of the Malawi haplochromine radiation. A. calliptera occupies a rich diversity of habitats, including Lake Malawi, as well as peripheral rivers and lakes (Parsons et al, 2017).…”

Astatotilapia species (Teleostei, Cichlidae) from Malawi, Mozambique and Tanzania, excluding the basin of Lake Victoria.

“…Collections at the type locality: Astatotilapia calliptera is well-known from many recent studies (e.g. Konings 2016;Nichols et al 2015;Parsons et al 2017;Peterson et al 2017;Tyers & Turner 2013) and appears to be more or less ubiquitous in shallow weedy areas in Lake Malawi and its catchment. A striking population with blue-grey adult males is reported from Chizumulu Island (Konings 2016), but other populations seem phenotypically quite similar, with males showing a spectacular multi-colouredlargely golden yellow -breeding dress (Figure 54-58).…”

Maternal mRNA input of growth and stress-response-related genes in cichlids in relation to egg size and trophic specialization

“…egg size and fecundity, in mouthbrooding cichlids were shown to evolve in parallel to different habitats across the 3 radiations [ 40 ]. It was also recently reported that various life-history traits such as clutch size and egg mass in a riverine haplochromine, Astatotilapia burtoni , were diverging at the population level, suggestive of ‘ongoing’ adaptive radiation [ 41 ]. Furthermore, haplochromines have evolved numerous trophic adaptations to acquire different food sources such as algae, snails, insects and shrimp [ 42 ].…”