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

Host-parasite dynamics involve coevolutionary arms races, which may lead to host specialization and ensuing diversification. Our general understanding of the evolution of host specialization in brood parasites is compromised by a restricted focus on bird and insect lineages. The cuckoo catfish (Synodontis multipunctatus) is an obligate parasite of parental care of mouthbrooding cichlids in Lake Tanganyika. Given the ecological and taxonomic diversity of mouthbrooding cichlids in the lake, we hypothesized the existence of sympatric host-specific lineages in the cuckoo catfish. In a sample of 779 broods from 20 cichlid species, we found four species parasitized by cuckoo catfish (with prevalence of parasitism of 2%-18%). All parasitized cichlids were from the tribe Tropheini, maternal mouthbrooders that spawn over a substrate (rather than in open water). Phylogenetic analysis based on genomic (ddRAD sequencing) and mitochondrial (Dloop) data from cuckoo catfish embryos showed an absence of host-specific lineages. This was corroborated by analyses of genetic structure and co-ancestry matrix. Within host species, parasitism was not associated with any individual characteristic we recorded (parent size, water depth), but was costly as parasitized parents carried smaller clutches of their own offspring. We conclude that the cuckoo catfish is an intermediate generalist and discuss costs, benefits and constraints of host specialization in this species and brood parasites in general.

Evolutionary Genomics at the Human-Environment Interface in Africa.

We report on the first meeting of SMBE in Africa. SMBE Malawi was initiated to bring together African and international researchers who use genetics or genomics to study natural systems impacted by human activities. The goals of this conference were 1) to reach a world-class standard of science with a large number of contributions from Africa, 2) to initiate exchange between African and international researchers, and 3) to identify challenges and opportunities for evolutionary genomics research in Africa. As repored, we think that we have achieved these goals and make suggestions on the way forward for African evolutionary genomics research.

Nest defense in the face of cuckoldry: evolutionary rather than facultative adaptation to chronic paternity loss.

BACKGROUND: Raising unrelated offspring is typically wasteful of parental resources and so individuals are expected to reduce or maintain low levels of parental effort when their parentage is low. This can involve facultative, flexible adjustments of parental care to cues of lost parentage in the current brood, stabilizing selection for a low level of paternal investment, or an evolutionary reduction in parental investment in response to chronically low parentage. RESULTS: We studied parental care in Variabilichromis moorii, a socially monogamous, biparental cichlid fish, whose mating system is characterized by frequent cuckoldry and whose primary form of parental care is offspring defense. We combine field observations with genetic parentage analyses to show that while both parents defend their nest against intruding con- and hetero-specifics, males and females may do so for different reasons. Males in the study group (30 breeding pairs) sired 0-100% (median 83%) of the fry in their nests. Males defended less against immediate threats to the offspring, and more against threats to their territories, which are essential for the males' future reproductive success. Males also showed no clear relationship between their share of defense and their paternity of the brood. Females, on the other hand, were related to nearly all the offspring under their care, and defended almost equally against all types of threats. CONCLUSION: Overall, males contributed less to defense than females and we suggest that this asymmetry is the result of an evolutionary response by males to chronically high paternity loss in this species. Although most males in the current study group achieved high parentage in their nests, the average paternity in V. moorii, sampled across multiple seasons, is only about 55%. We highlight the importance and complexity of studying nest defense as a form of parental care in systems where defense may serve not only to protect current offspring, but also to ensure future reproductive success by maintaining a territory.

Seasonal variation in cuckoldry rates in the socially monogamous cichlid fish Variabilichromis moorii.

Mating patterns in animal populations can respond to environmental conditions and consequently vary across time. To examine this variation in nature, studies must include temporal replicates from the same population. Here, we report temporal variation in genetic parentage in the socially monogamous cichlid Variabilichromis moorii from Lake Tanganyika, using samples of broods and their brood-tending parents that were collected across five field trips from the same study population. The sampled broods were either spawned during the dry season (three field trips) or during the rainy season (two trips). In all seasons, we detected substantial rates of extra-pair paternity, which were ascribed to cuckoldry by bachelor males. Paternity shares of brood-tending males were consistently higher, and the numbers of sires per brood were consistently lower, in broods that were spawned in the dry seasons compared to broods from the rainy seasons. In contrast, the strength of size-assortative pairing in our V. moorii population did not vary temporally. Seasonal fluctuations in environmental conditions, such as water turbidity, are proposed as a mechanism behind variable cuckolder pressure. Our data demonstrate the utility of long-term monitoring to improve our understanding of animal mating patterns. Supplementary Information: The online version contains supplementary material available at 10.1007/s10750-022-05042-0.

An extant cichlid fish radiation emerged in an extinct Pleistocene lake.

The haplochromine cichlid fish of the East African Great Lakes represent some of the fastest and most species-rich adaptive radiations known, but rivers in most of Africa accommodate only a few morphologically similar species of haplochromine cichlid fish. This has been explained by the wealth of ecological opportunity in large lakes compared with rivers. It is therefore surprising that the rivers of southern Africa harbour many, ecologically diverse haplochromines. Here we present genetic, morphological and biogeographical evidence suggesting that these riverine cichlids are products of a recent adaptive radiation in a large lake that dried up in the Holocene. Haplochromine species richness peaks steeply in an area for which geological data reveal the historical existence of Lake palaeo-Makgadikgadi. The centre of this extinct lake is now a saltpan north of the Kalahari Desert, but it once hosted a rapidly evolving fish species radiation, comparable in morphological diversity to that in the extant African Great Lakes. Importantly, this lake seeded all major river systems of southern Africa with ecologically diverse cichlids. This discovery reveals how local evolutionary processes operating during a short window of ecological opportunity can have a major and lasting effect on biodiversity on a continental scale.

Palaeoplex gen. nov. and Lufubuchromis gen. non, two new monotypic cichlid genera (Teleostei: Cichlidae) from northern Zambia.

Two monotypic haplochromine cichlid genera (Teleostei: Cichlidae) of the Pseudocrenilabrus group are described from northern Zambia. One new genus is Palaeoplex gen. nov., with Pa. palimpsest sp. nov. as the type species, from the Luongo and Kalungwishi Rivers (Upper Congo drainage, Luapula subdrainage). It is diagnosed by a unique combination of morphological characters: (1) a fully developed infraorbital series without a distinct gap between the lachrymal and second infraorbital bone, (2) fused hypuralia 1+2 and hypuralia 3+4, (3) molariform teeth on the sagittal series of the lower pharyngeal jaw, and (4) a large maximum size. The second new genus, Lufubuchromis gen. nov., with L. relictus sp. nov. as the type species, is restricted to the upper Lufubu River catchment (Upper Congo drainage, Lake Tanganyika subdrainage). It is diagnosed by a unique combination of morphological characters: (1) a fully developed infraorbital series without a distinct gap between the lachrymal and second infraorbital bone, (2) fused hypuralia 1+2 (rarely with a visible suture) and fused hypuralia 3+4, (3) a unique male coloration pattern, i.e. deep crimson red colored areas on the anterior ventral flank parts, chest and belly and on the lower head; remaining parts of flanks and caudal peduncle bluish), and (4) a Pseudocrenilabrus blotch present in both sexes. Both new genera are compared with all remaining taxa of the Pseudocrenilabrus group and with all representatives of all other major haplotilapiine lineages.

Orthohantaviruses, Emerging Zoonotic Pathogens.

Orthohantaviruses give rise to the emerging infections such as of hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) in Eurasia and the Americas, respectively. In this review we will provide a comprehensive analysis of orthohantaviruses distribution and circulation in Eurasia and address the genetic diversity and evolution of Puumala orthohantavirus (PUUV), which causes HFRS in this region. Current data indicate that the geographical location and migration of the natural hosts can lead to the orthohantaviruses genetic diversity as the rodents adapt to the new environmental conditions. The data shows that a high level of diversity characterizes the genome of orthohantaviruses, and the PUUV genome is the most divergent. The reasons for the high genome diversity are mainly caused by point mutations and reassortment, which occur in the genome segments. However, it still remains unclear whether this diversity is linked to the disease's severity. We anticipate that the information provided in this review will be useful for optimizing and developing preventive strategies of HFRS, an emerging zoonosis with potentially very high mortality rates.

The coincidence of ecological opportunity with hybridization explains rapid adaptive radiation in Lake Mweru cichlid fishes.

The process of adaptive radiation was classically hypothesized to require isolation of a lineage from its source (no gene flow) and from related species (no competition). Alternatively, hybridization between species may generate genetic variation that facilitates adaptive radiation. Here we study haplochromine cichlid assemblages in two African Great Lakes to test these hypotheses. Greater biotic isolation (fewer lineages) predicts fewer constraints by competition and hence more ecological opportunity in Lake Bangweulu, whereas opportunity for hybridization predicts increased genetic potential in Lake Mweru. In Lake Bangweulu, we find no evidence for hybridization but also no adaptive radiation. We show that the Bangweulu lineages also colonized Lake Mweru, where they hybridized with Congolese lineages and then underwent multiple adaptive radiations that are strikingly complementary in ecology and morphology. Our data suggest that the presence of several related lineages does not necessarily prevent adaptive radiation, although it constrains the trajectories of morphological diversification. It might instead facilitate adaptive radiation when hybridization generates genetic variation, without which radiation may start much later, progress more slowly or never occur.

Age and spread of the haplochromine cichlid fishes in Africa.

The Haplochromini are by far the most species-rich cichlid fish tribe that originated along with the so-called primary radiation of the Lake Tanganyika cichlid species flock, i.e. at the same time during which the majority of the endemic Lake Tanganyika cichlid tribes emerged. Unlike the other tribes, the haplochromines are not restricted to Lake Tanganyika but distributed throughout Africa, except for the northwestern part of the continent. Haplochromine cichlids seeded the adaptive radiation of cichlid fishes in Lakes Malawi, Kivu, Victoria, Turkana, as well as in the now extinct paleo-Lake Makgadikgadi. Here we present a comprehensive phylogenetic and phylogeographic analysis of haplochromine cichlids that is based upon DNA sequences of two mitochondrial gene segments of riverine taxa covering all major African biogeographic regions where haplochromines are found. Our analysis revealed that six lineages of haplochromines originated within a short period of time, about 5.3-4.4 MYA. These haplochromine lineages show a highly complex phylogeographic pattern, probably severely influenced by climate- and/or geology-induced changes of the environment, with river capture events most likely playing an important role for species dispersal.

Mitochondrial genome annotation and phylogenetic placement of Oreochromis andersonii and O. macrochir among the cichlids of southern Africa.

Genetic characterization of southern African cichlids has not received much attention. Here, we describe the mitogenome sequences and phylogenetic positioning of Oreochromis andersonii and O. macrochir among the African cichlids. The complete mitochondrial DNA sequences were determined for O. andersonii and O. macrochir, two important aquaculture and fisheries species endemic to southern Africa. The complete mitogenome sequence lengths were 16642 bp and 16644 bp for O. andersonii and O. macrochir respectively. The general structural organization follows that of other teleost species with 13 protein-coding genes, 2 rRNAs, 22 tRNAs and a non-coding control region. Phylogenetic placement of the two species among other African cichlids was performed using Maximum Likelihood (ML) and Bayesian Markov-Chain-Monte-Carlo (MCMC). The consensus trees confirmed the relative positions of the two cichlid species with O. andersonii being very closely related to O. mossambicus and O. macrochir showing a close relation to both species. Among the 13 mitochondrial DNA protein coding genes ND6 may have evolved more rapidly and COIII was the most conserved. There are signs that ND6 may have been subjected to positive selection in order for these cichlid lineages to diversify and adapt to new environments. More work is needed to characterize the southern Africa cichlids as they are important species for capture fisheries, aquaculture development and understanding biogeographic history of African cichlids. Bio-conservation of some endangered cichlids is also essential due to the threat by invasive species.

A new species of Pseudocrenilabrus (Perciformes: Cichlidae) from Lake Mweru in the Upper Congo River System.

Pseudocrenilabrus pyrrhocaudalis sp. nov. is described from Lake Mweru in the upper Congo River drainage, on the border of the Democratic Republic of Congo and Zambia. This species, which appears to be endemic to the lake, lives in sympatry with P. philander. Pseudocrenilabrus pyrrhocaudalis sp. nov. is distinguished from P. philander in nuptial males by the presence of an orange colour on the ventral part of the body and the proximal parts of the anal and caudal fins, a broad band of bright white on the distal edge of anal and caudal fins, a uniform grey head and dorsum, and a subtruncate caudal fin. In addition, P. pyrrhocaudalis has a shorter snout, a narrower head, a smaller interorbital distance, a smaller pre-anal distance, a more slender caudal peduncle and fewer scales around the caudal peduncle in both sexes.

Evolutionary history and biogeographic affinities of the serranochromine cichlids in Zambian rivers.

Zambian rivers belong to two major drainages: the Luapula-Congo and the Zambezi River system. Tectonic activity repeatedly altered drainage systems in Africa, so that current fish faunas can only be understood in the context of historic drainage capture events. We use phylogenetic relationships of one widespread lineage of haplochromine cichlids, the serranochromines, to trace their biogeographic expansion and diversification in Zambia. The mitochondrial DNA phylogeny suggests five ancient clades, and their common ancestor was likely to have invaded from the Lower Congo River. The branching intervals in the linearized tree analysis suggest three major cladogenesis events and two periods of faunal exchange. The five clades originating in the Congo River drainage diversified further; one stayed in the Congo drainage, one diversified in the Zambezi system only, while the three clades of mixed distribution underwent diversification in the Zambezi system, to re-enter the Congo drainage very recently, as indicated by sometimes zero mutation differences among taxa from different drainages. Our hypothesis is consistent with the suggested radiation in the extinct Lake palaeo-Makgadikgadi, so that we propose that the Zambian serranochromine fauna in part represents survivors of the extinct lacustrine flock plus several novel species that originated in situ.

Ancient divergence in bathypelagic lake tanganyika deepwater cichlids: mitochondrial phylogeny of the tribe bathybatini.

The cichlid species flock of Lake Tanganyika represents a polyphyletic assemblage of eight ancestral lineages, which colonized the emerging lake independently. Our study is focused on one of these lineages, the Bathybatini, a tribe of specialized piscivorous cichlids of the deep pelagic zone. By analyzing three mtDNA gene segments of all eight species of the tribe and two species of the closely related Trematocarini, we propose on the basis of a linearized tree analysis that the Bathybatini comprise two distinct lineages, the genera Hemibates and Bathybates, that seeded the primary lacustrine Tanganyika radiation independently. The genus Hemibates is likely to represent a distinct lineage that emerged simultaneously with the tribe Trematocarini and the genus Bathybates and should be therefore treated as a distinct tribe. Within the genus Bathybates, B. minor clearly represents the most ancestral split and is likely to have diverged from the remaining species in the course of the "primary lacustrine Tanganyika radiation" during which also the radiations of the Lamprologini and the H-lineage took place. The remaining "large" Bathybates species also diversified almost simultaneously and in step with the diversification of other Tanganyikan lineages-the Limnochromini and Cyprichromini-with B. graueri occupying the most ancestral branch, suggesting that these were induced by the same environmental changes. The lack of geographic color morphs suggests that competition and resource partitioning, rather than allopatric speciation, promoted speciation within the genus Bathybates.