Contrasting geographic structure in evolutionarily divergent Lake Tanganyika catfishes

Abstract

Geographic isolation is suggested to be among the most important processes in the generation of cichlid fish diversity in East Africa's Great Lakes, both through isolation by distance and fluctuating connectivity caused by changing lake levels. However, even broad scale phylogeographic patterns are currently unknown in many non‐cichlid littoral taxa from these systems. To begin to address this, we generated restriction‐site‐associated DNA sequence (RADseq) data to investigate phylogeographic structure throughout Lake Tanganyika (LT) in two broadly sympatric rocky shore catfish species from independent evolutionary radiations with differing behaviors: the mouthbrooding claroteine, Lophiobagrus cyclurus, and the brood‐parasite mochokid, Synodontis multipunctatus. Our results indicated contrasting patterns between these species, with strong lake‐wide phylogeographic signal in L. cyclurus including a deep divergence between the northern and southern lake basins. Further structuring of these populations was observed across a heterogeneous habitat over much smaller distances. Strong population growth was observed in L. cyclurus sampled from shallow shorelines, suggesting population growth associated with the colonization of new habitats following lake‐level rises. Conversely, S. multipunctatus, which occupies a broader depth range, showed little phylogeographic structure and lower rates of population growth. Our findings suggest that isolation by distance and/or habitat barriers may play a role in the divergence of non‐cichlid fishes in LT, but this effect varies by species.

Recent lake expansion triggered the adaptive radiation of freshwater snails in the ancient Lake Biwa

“…This pattern was also reported in a shallow water catfish in Lake Tanganyika (Peart et al. ). Similar to the case of the cichlids and catfish in African ancient lakes, the geographic distribution of nine Biwamelania species is confined to small regions in the lake (Watanabe and Nishino , see Fig.…”

“…Indeed, many cichlids are narrow endemics present only in a single stretch of continuous habitat (Ribbink et al 1983) and exhibited low level of gene flow among local populations (Genner et al 2010). This pattern was also reported in a shallow water catfish in Lake Tanganyika (Peart et al 2018). Similar to the case of the cichlids and catfish in African ancient lakes, the geographic distribution of nine Biwamelania species is confined to small regions in the lake (Watanabe and Nishino 1995, see ) morii, inhabit only isolated islets in the lake (Fig.…”

Lack of host specialization despite selective host use in brood parasitic cuckoo catfish

“…The strength of host defence depends on abundance and virulence of parasitism (Bush et al., 2019). Cuckoo catfish are abundant throughout Lake Tanganyika (Peart et al., 2018; Wright & Page, 2006), including our study site. Parasitized host cichlids commonly lose their own brood entirely (25% in Sato (1986), 21% in the present study) and a prevalence of 18% parasitized broods of S. diagramma appears relatively high.…”

“…Young catfish hatch earlier than their hosts and feed on the host embryos (Cohen et al., 2019), often resulting in complete failure of host brood (Blažek et al., 2018; Sato, 1986). The cuckoo catfish is a common benthic species with lake‐wide occurrence (Peart et al., 2018) and is associated with various substrate types, although it is most common in rocky habitats (Wright & Page, 2006). It is known to naturally parasitize at least eight cichlid species.…”