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opencc-zeroDec 2015View details →

Data from: Genetic evidence for prevalence of alloparental care in a socially monogamous biparental cichlid fish, Perissodus microlepis, from Lake Tanganyika supports the "selfish shepherd effect" hypothesis

Alloparental care – care for unrelated young – is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi-parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra-pair paternity and extra-pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming-out and fostering behaviors. In the majority of broods, the sizes of the parents' own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the 'selfish shepherd effect' hypothesis, i.e., that foster parents preferentially accept unrelated "smaller or not larger" young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming-out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.

opencc-zeroDec 2011View details →

Data from: Parsing parallel evolution: ecological divergence and differential gene expression in the adaptive radiations of thick-lipped Midas cichlid fishes from Nicaragua

The study of parallel evolution facilitates the discovery of common rules of diversification. Here, we examine the repeated evolution of thick lips in Midas cichlid fishes (the Amphilophus citrinellus species complex)—from two Great Lakes and two crater lakes in Nicaragua—to assess whether similar changes in ecology, phenotypic trophic traits and gene expression accompany parallel trait evolution. Using next-generation sequencing technology, we characterize transcriptome-wide differential gene expression in the lips of wild-caught sympatric thick- and thin-lipped cichlids from all four instances of repeated thick-lip evolution. Six genes (apolipoprotein D, myelin-associated glycoprotein precursor, four-and-a-half LIM domain protein 2, calpain-9, GTPase IMAP family member 8-like and one hypothetical protein) are significantly underexpressed in the thick-lipped morph across all four lakes. However, other aspects of lips' gene expression in sympatric morphs differ in a lake-specific pattern, including the magnitude of differentially expressed genes (97-510). Generally, fewer genes are differentially expressed among morphs in the younger crater lakes than in those from the older Great Lakes. Body shape, lower pharyngeal jaw size and shape, and stable isotopes (δ13C and δ15N) differ between all sympatric morphs, with the greatest differentiation in the Great Lake Nicaragua. Some ecological traits evolve in parallel (those related to foraging ecology; e.g. lip size, body and head shape) but others, somewhat surprisingly, do not (those related to diet and food processing; e.g. jaw size and shape, stable isotopes). Taken together, this case of parallelism among thick- and thin-lipped cichlids shows a mosaic pattern of parallel and nonparallel evolution.

opencc-zeroJul 2021View details →

Data from: Where Am I? Niche constraints due to morphological specialisation in two Tanganyikan cichlid fish species

Food resource specialisation within novel environments is considered a common axis of diversification in adaptive radiations. Feeding specialisations are often coupled with striking morphological adaptations and exemplify the relation between morphology and diet (phenotype-environment correlations), as seen in, for example, Darwin finches, Hawaiian spiders and, in particular, the cichlid radiations in East Africa. The cichlids' potential to rapidly exploit and occupy a variety of different habitats has previously been attributed to the variability and adaptability of their trophic structures including the pharyngeal jaw apparatus. Here we report a reciprocal transplant experiment designed to explore the adaptability of the cichlid's trophic structures in highly specialised cichlid fish species. More specifically, we forced two common but ecologically distinct cichlid species from Lake Tanganyika, Tropheus moorii (rock-dweller) and Xenotilapia boulengeri (sand-dweller), to live on their preferred as well as on an un-preferred habitat (sand and rock, respectively). We measured their overall performance on the different habitat types and explored whether adaptive phenotypic plasticity is involved in adaptation. We found that, while habitat had no effect on the performance of X. boulengeri, T. moorii performed significantly better in its preferred habitat. Despite an experimental duration of several months we did not find a shift in the morphology of the lower pharyngeal jaw bone that would be indicative of adaptive phenotypic plasticity in this trait.

opencc-zeroJul 2021View details →

Pervasive admixture and the spread of a large-lipped form in a cichlid fish radiation

Adaptive radiations have proven important for understanding the mechanisms and processes underlying biological diversity. The convergence of form and function, as well as admixture and adaptive introgression, are common in adaptive radiations. However, distinguishing between these two scenarios remains a challenge for evolutionary research. The Midas cichlid species complex (Amphilophus spp.) is a prime example of adaptive radiation, with phenotypic diversification occurring at various stages of genetic differentiation. One species, A. labiatus, has large fleshy lips, is associated with rocky lake substrates, and occurs patchily within Lakes Nicaragua and Managua. By contrast, the similar, but thin-lipped, congener, A. citrinellus, is more common and widespread. We investigated the evolutionary history of the large-lipped form, specifically regarding whether the trait has evolved independently in both lakes from ancestral thin-lipped populations, or via dispersal and/or admixture events. We collected samples from distinct locations in both lakes, and assessed differences in morphology and ecology. Using RAD-seq, we genotyped thousands of SNPs to measure population structure and divergence, demographic history, and admixture. We found significant between-species differences in ecology and morphology, local intraspecific differences in body shape and trophic traits, but only limited intraspecific variation in lip shape. Despite clear ecological differences, our genomic approach uncovered pervasive admixture between species and low genomic differentiation, with species within lakes being genetically more similar than species between lakes. Taken together, our results suggest a single origin of large-lips, followed by pervasive admixture and adaptive introgression, with morphology being driven by local ecological opportunities, despite on-going gene-flow.

opencc-zeroAug 2021View details →

Data from: Intra-sexual selection: kin competition increases male-male territorial aggression in a monogamous cichlid fish

During intrasexual competition, individuals of the same sex compete for access to breeding sites and mating partners, often accompanied by aggressive behavior. Kin selection theory predicts different kin directed social interactions ranging from cooperation to aggression depending on the context and the resource in question. Kin competition reducing indirect fitness might be avoided by actively expelling relatives from territories and by showing higher aggression against kin. The West-African cichlid Pelvicachromis taeniatus is a monogamous cave breeder with males occupying and defending breeding sites against rivals. This species is capable of kin recognition and shows kin-preference during juvenile shoaling and mate choice. However, sub-adults of P. taeniatus seem to avoid the proximity of same-sex kin. In the present study, we examined territorial aggression of territory holders against intruding related and unrelated males as well as intruder's behavior. We observed higher aggression among related competitors suggesting that related males are less tolerated as neighbors. Avoidance of intra-sexual competition with relatives might increase indirect fitness of males in monogamous species.

FIGURE 8 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 8. Eastern part of Kamamba Island, type locality of Lepidiolamprologus kamambae. Photo by Mikael Karlsson and Magnus Karlsson, 30 April 2008.

FIGURE 5 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 5. Lepidiolamprologus kamambae. Living specimen, not preserved, photographed in natural habitat at Kamamba Island, 15 m depth. Photo by Mikael Karlsson and Magnus Karlsson, 30 April 2008.

FIGURE 3. Lepidiolamprologus kamambae. Holotype, NRM 61943, 137.2 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 3. Lepidiolamprologus kamambae. Holotype, NRM 61943, 137.2 mm SL. A. Lateral aspect of snout. B. frontal aspect of snout. C. dorsal aspect of head.

FIGURE 2 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 2. Lepidiolamprologus kamambae. Lower pharyngeal jaw in occlusal (upper) and approximately lateral (lower) aspect. Scale for occlusal aspect. From paratype NRM 51558, 122.1 mm SL.

FIGURE 7 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 7. Outline map of Lake Tanganyika showing collecting localities of L. kamambae and comparative material of L. elongatus, L. kendalli, L. mimicus, and L. profundicola.

FIGURE 1 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 1. Preserved specimens, all from Tanzania, Lake Tanganyika. A. Lepidiolamprologus kamambae, holotype, NRM 61943, 137.2 mm SL, Kamamba Island. B. L. kendalli, NRM 51590, 100.5 mm SL, Muzi. C. L. elongatus, NRM 59555, 116.4 mm SL, Udachi. D. L. mimicus, NRM 51595, 126.7 mm SL, Frontosa Reef.

FIGURE 4 in Lepidiolamprologus kamambae, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika

FIGURE 4. Living specimens photographed in the field, showing live colors, all from Tanzania, Lake Tanganyika. A. Lepidiolamprologus kamambae, paratype, NRM 51558, 135.2 mm SL, Kamamba Island. B. L. kendalli, NRM 51544, 124.0 mm SL, Muzi. C. L. elongatus, NRM 59555, 150.1 mm SL, Udachi. D. L. profundicola, NRM 61570, 260.9 mm SL, Kansombo. Photographs by Mikael Karlsson and Magnus Karlsson.

opencc-zeroAug 2023View details →

Data from: Phenotypic rate and state are decoupled in response to river-to-lake transitions in cichlid fishes

Geographic access to isolated ecosystems is an important catalyst of adaptive radiation. Cichlid fishes repeatedly colonized rift, crater, and volcanic lakes from surrounding rivers. We test the "lake effect" on the phenotypic rate and state across 253 cichlid species. The rate of evolution was consistently higher (~10-fold) in lakes, and consistent across different dimensions of the phenotype. Rate shifts tended to occur coincident with or immediately following river-to-lake transitions, generally resulting in 2- to 5-fold faster rates than in the founding riverine lineage. By contrast, river- and lake-dwelling cichlids exhibit considerable overlap in phenotypes, generally with less disparity in lakes, but often different evolutionary optima. Taken together, these results suggest that lake radiations rapidly expand into niches largely already represented by ancestral riverine lineages, albeit in different frequencies. Lakes may provide ecological opportunity via ecological release (e.g., from predators/competitors), but need not be coupled with access to novel ecological niches.