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Female mate choice has strong experimental support as a diversifying force in the speciation of the haplochromine cichlid fishes of Lake Malaŵi, Africa. Somewhat less understood is the role that male-male aggression might have played in the evolution of new species of these fishes. In the rock-dwelling haplochromines of Lake Malaŵi, primarily territory-holding males successfully court females; by determining which males gain territories, male-male aggression could support speciation by excluding less-fit males from the breeding population. To test the hypothesis that males should direct more aggression towards conspecific rivals, the aggression directed towards conspecific and heterospecific opponents was compared in a sympatric pair of cichlids of the genus Labeotropheus Ahl 1927 (Labeotropheus fuelleborni Ahl 1927 and Labeotropheus trewavasae Fryer 1956). It was found that when presented with a pair of rivals, males of both species did direct more aggression towards the conspecific opponent, and the amount of aggression increased when the conspecific opponent was larger than the heterospecific opponent. In addition, this study found a difference in the behavioural repertoire of the species: L. fuelleborni tends to rely on displays to intimidate opponents, whereas L. trewavasae employs more physical attacks to drive away opponents. Males of both species can thus recognize conspecifics and assess an opponent's relative threat to their ability to successfully reproduce, and use species-specific strategies to intimidate opponents.

Lake Malaŵi cichlids have evolved rapidly, extensively, and in some cases iteratively to fill an array of ecological niches; however, neither species richness nor trophic diversity is distributed equally across lineages. In the context of evolutionary theory, such differences offer predictions about the magnitudes and patterns of morphological variation within lineages. In this paper, we use geometric morphometrics in three prevalent rock-dwelling genera to address questions related to morphological diversity, disparity, integration, and modularity. In particular, we focus on comparisons between the highly specialized and species-poor genus, Labeotropheus (Ahl in Sitzungsberichte der Berlinische Gesellschaft Naturforschender Freunde zu Berlin 1926:51–62, 1927), and the more ecologically diverse and species-rich genus, Tropheops (Trewavas in Revue Francaise d’Aquariologie Herpetologie 10:97–106, 1984), as well as between species with lake-wide versus more limited distributions. We find that Labeotropheus exhibits comparable levels of morphological disparity to Tropheops, which suggests that a specialized foraging mode has not constrained cranial variability in this genus. We also find that species with a lake-wide distribution exhibit levels of disparity three times greater than that in a species with a limited distribution. Finally, we show that magnitudes of integration and patterns of modularity are lineage specific, and do not directly correspond to ecology. In sum, these data provide insights into the complex relationship between ecology, morphological variability, and evolvability.

Labeotropheus is a genus of haplochromine cichlids endemic to Lake Malaŵi, Africa. Since its original description, surprisingly few additional species have been described, largely due to a misinterpretation of the historical taxonomic treatment of allopatric populations of Labeotropheus. Previously published evidence of genetic and morphological divergence among southern populations of Labeotropheus suggests that species diversity is underestimated. Morphometric, meristic, and color characteristics are employed to describe a new species of Labeotgropheus endemic to Mumbo Island and Thumbi West Island near the Nankumba Peninsula in southern Lake Malaŵi. The new species is distinguished from congeners by a wider body, longer pectoral fins, a shorter snout, and male nuptial coloration.

The haplochromine cichlid genus Labeotropheus is endemic to Lake Malaŵi, Africa. This genus presently contains two recognized species, Labeotropheus fuelleborni and L. trewavasae. As currently recognized, both species consist of geographically isolated populations scattered throughout the lake, each distinguished by a unique male nuptial color pattern. While other such allopatric populations of Lake Malaŵi cichlids have been described as different species, those of Labeotropheus have not, largely due to misunderstandings or misinterpretations of criteria applied to other Malaŵian endemics. Taking a refined approach to the recognition of putative species of Labeotropheus, I used morphometric, meristic, and color characteristics to describe two new, very similarly colored, species of Labeotropheus, both of which are found near Katale Island alongside the Luromo Peninsula in northwestern Lake Malaŵi.

The cichlid fishes of Lake Malaŵi are the paramount example of adaptive radiation in vertebrates. Evidence of their astounding diversity is perhaps most visible in their adaptations for obtaining food; the genus Labeotropheus, due to their prominent snouts, are an interesting example of an extreme adaptation for feeding. Two different body types are found in this genus: a deep-bodied form (e.g., L. fuelleborni) found most often in turbulent shallow water; and a slender bodied form (e.g., L. trewavasae) found in structurally-complex deep water habitats. Here we test the hypothesis that L. trewavasae should suffer a loss in fitness, measured as growth rate, if raised in turbulence; additionally, we examined growth and morphology of L. fuelleborni and L. fuelleborni x L. trewavasae hybrids under these conditions. We did find the predicted loss of fitness in turbulent-raised L. trewavasae, but found no loss of fitness for L. fuelleborni in either condition; hybrids, due to an unusual morphology, performed better in turbulent as opposed to control conditions. Fitness in turbulent conditions was dependent upon morphology, with deeper bodies and upturned neurocrania allowing a greater growth rate under these conditions. Directional selection on morphology was crucial in the evolution of morphology in the Labeotropheus.

The Lake Malawi cichlid genus Labeotropheus has been a source of confusion among biologists and taxonomists. Although unique populations of both L. fuelleborni and L. trewavasae exist throughout the lake, these populations have not been elevated to species, despite taxonomists doing so for populations within other Lake Malawi cichlids. One reason for this oversight is the supposed consistent differences in morphology between Labeotropheus species; since, where they co-occur, L. fuelleborni is always deeper-bodied than L. trewavasae, it is thought that all deep-bodied populations of Labeotropheus are L. fuelleborni, and the slender ones are L. trewavasae. Using geometric morphometrics, we analyze 18 populations of Labeotropheus and show that body shape varies among populations, and does not always fall into a deep-body/slender-body dichotomy. These differences in body shape are not related to geographical distance among populations, but are possibly related to the type of habitat in which the populations are found. Further, head shape is extremely variable among populations, and we find two locations where there is convergence in head shape between sympatric L. fuelleborni and L. trewavasae. Our results suggest that the morphological criteria applied to the Labeotropheus are not accurate, and hamper the recognition of Labeotropheus biodiversity.

Nine members of the Neotropical treeboa genus Corallus occur from Guatemala to south-eastern Brazil and recent studies have provided an inconclusive picture about the relationship between morphology and trophic ecology in these snakes. To construct a more complete picture, we conducted the first study of morphology and diet to consider all nine species. Using adult specimens from museum collections, we examined several morphometric and meristic variables and their possible relationship to Corallus diets. Broadly, we found three basic morphologies within the genus: a short, narrow head and a slender body (C. cookii, C. grenadensis, C. hortulanus, and C. ruschenbergerii), useful for exploiting a wide variety of prey; a relatively stout body with a long, wide head (C. batesii, C. caninus, and C. cropanii) associated with feeding on larger mammalian prey; and an intermediate morphology, found in C. annulatus and C. blombergii, which may be indicative of endotherm generalists. These morphological and dietary patterns exhibit a strong degree of congruence with a recent molecular phylogeny of Corallus and highlight a heretofore unexamined ecological diversification within Corallus. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 466–475.

For evolutionary ecologists, the holy grail of visual ecology is to establish an unambiguous link between photoreceptor sensitivity, the spectral environment, and the perception of specific visual stimuli (e.g., mates, food, predators, etc.). Due to the bright nuptial colors of the males, and the role female mate choice plays in their evolution, the haplochromine cichlid fishes of the African great lakes are favorite research subjects for such investigations. Despite this attention, current evidence is equivocal; while distinct correlations among photoreceptor sensitivity, photic environment, and male coloration exist in Lake Victorian haplochromines, attempts to find such correlations in Lake Malawian cichlids have failed. Lake Malawi haplochromines have a wide variability in their short-wavelength-sensitive photoreceptors, especially compared to their mid- and long-wavelength-sensitive photoreceptors; these cichlids also vary in the degree to which they express one of three basic color patterns (vertical bars, horizontal stripes, and solid patches of colors), each of which is likely used in a different form of communication. Thus, we hypothesize that, in these fishes, spectral sensitivity and color pattern have evolved in a correlated fashion to maximize visual communication; specifically, ultraviolet sensitivity should be found in vertically-barred species to promote ‘private’ communication, while striped species should be less likely to have ultraviolet sensitivity, since their color pattern carries ‘public’ information. Using phylogenetic independent contrasts, we found that barred species had strong sensitivity to ultraviolet wavelengths, but that striped species typically lacked sensitivity to ultraviolet light. Further, the only variable, even when environmental variables were simultaneously considered, that could predict ultraviolet sensitivity was color pattern. We also found that, using models of correlated evolution, color pattern and ultraviolet sensitivity are correlated in Lake Malawi cichlid evolution, with the likely ancestor being a vertically-barred, ultraviolet-sensitive species, the descendants of which lost both ultraviolet sensitivity and a barred color pattern. These results, indicating that communication of ‘public’ and ‘private’ signals is mediated via differing perceptions of color patterns, suggest a functional connection between visual sensitivity and colour pattern, a novel finding in Lake Malawi cichlids.

Nine species of the Neotropical boid genus Corallus are distributed from southeastern Guatemala to southeastern Brazil. Based largely on previously published papers, we accumulated 271 prey records for all species combined, and they comprised 2 frogs, 69 lizards (mostly Anolis), 1 snake, 65 birds, and 134 mammals (marsupials, rodents, bats). There is a conspicuous difference in diet between the two West Indian species (C. cookii and C. grenadensis) and species occurring on the mainland: juvenile and subadult boas from the West Indies prey almost entirely on anoles, whereas on the mainland (with the notable exceptions of C. batesii and C. caninus), those age classes prey largely on birds and bats. Four species (C. cookii, C. grenadensis, C. hortulanus, and C. ruschenbergerii) are vertebrate generalists and exhibit both active and ambush foraging modes. Adult C. batesii and C. caninus (and, perhaps, C. cropanii) are specialists on mammalian prey, may only utilize an ambush foraging mode, and were ...

The discovery of melanopsin, the non-visual opsin present in intrinsically photosensitive retinal ganglion cells (ipRGCs), has created great excitement in the field of circadian biology. Now, researchers have emphasized melanopsin as the main photopigment governing circadian activity in vertebrates. Circadian biologists have tested this idea under standard laboratory, 12h Light: 12h Dark, lighting conditions that lack the dramatic daily colour changes of natural skylight. Here we used a stimulus paradigm in which the colour of the illumination changed throughout the day, thus mimicking natural skylight, but luminance, sensed intrinsically by melanopsin containing ganglion cells, was kept constant. We show in two species of cichlid, Aequidens pulcher and Labeotropheus fuelleborni, that changes in light colour, not intensity, are the primary determinants of natural circadian activity. Moreover, opponent-cone photoreceptor inputs to ipRGCs mediate the sensation of wavelength change, and not the intrinsic photopigment, melanopsin. These results have implications for understanding the evolutionary biology of non-visual photosensory pathways and answer long-standing questions about the nature and distribution of photopigments in organisms, including providing a solution to the mystery of why nocturnal animals routinely have mutations that interrupt the function of their short wavelength sensitive photopigment gene.

– The role of male colouration in the behavioural interactions of haplochromine cichlids has received much attention. Previous studies supported the role played by visual signals during interactions of rock-dwelling cichlids, or mbuna, from Lake Malawi. It has largely been assumed that hue, and not pattern, is the primary signal encoded in male colouration; thus, the role of colour pattern has received less attention. We explored the use of visual signals during aggression in Labeotropheus fuelleborni by using identically and differently coloured opponents and by offering these opponents under coloured illumination. We presented two simultaneous opponents to males and found that the focal male’s responses depended upon opponent colour pattern; similarly patterned opponents received more aggression, even if presented under a hue-obscuring light source. These results support findings that gross colour pattern may be more important than hue in interactions among the mbuna and further support an important role for visual communication in these fishes.

Sexual selection via female mate choice is thought to have played a key role in the speciation of haplochromine cichlids, but a dominant role for visual signals in such processes has lately been called into question. In addition, the possible role of male mating preferences in haplochromine speciation has been little studied. We studied patterns of both female and male mate choice, based exclusively on visual signals, in order to evaluate potential reproductive isolation between two populations of the Lake Malawi haplochromine Labeotropheus fuelleborni. In the first experiment, females were allowed to choose between two males, one from the same population and the other allopatric with respect to the female. Females in this experiment responded more frequently to males from their own population. Similarly, the males in these trials displayed more frequently when presented with females of their own population. In the second experiment, a female was allowed to choose between two males, either both from her own population or both allopatric. In these trials, both males and females from the Katale population interacted significantly more frequently in settings in which all three individuals were from the same population (“same-population trios”), and those from the Chipoka population showed a similar trend. Thus, patterns in both male and female courtship behavior suggest that visual signals contribute to at least incipient reproductive isolation between populations of L. fuelleborni.

While the debate over species concepts and criteria affects all organisms on Earth, no group of organisms demonstrates a need for a consilient, universal species concept better than the haplochromine cichlids of Lake Malawi. These fishes, which are the single greatest radiation of vertebrates on the planet, are a daunting taxonomic puzzle for ichthyologists and evolutionary biologists who try to piece together the history and diversity of these fishes. Accordingly, a number of attempts to apply species concepts to these fishes have been attempted, though rarely with a satisfactory outcome. Focusing on the rock-dwelling cichlids, or mbuna, of Lake Malawi, I evaluate the species concepts that have been applied to these fishes, and conclude that the consilient formulation of the Evolutionary Species Concept is the most appropriate species concept to apply to both our current understanding of the mbuna, and future investigations of mbuna speciation and taxonomy. To further demonstrate the applicability and utility of the Evolutionary Species Concept, I provide a closer examination of the genus Labeotropheus, which has been overlooked in recent taxonomic investigations of the mbuna. While most other mbuna genera have had additional, formally described species added to them, if not additional provisionally named species, Labeotropheus has been ignored, largely due to inappropriately applied species concepts and criteria. I provide a possible research program for the Labeotropheus, based on the consilient formulation of the Evolutionary Species Concept, culminating in the description of new species.

A survey of stream fish communities was conducted in the upper Des Plaines River watershed in Illinois and Wisconsin to determine the distribution of fish species and to evaluate the effects of tributary spatial position, urbanization, and multiple low-head dams on fish species diversity and species composition. Forty-eight sites upstream of Salt Creek in Illinois to the headwaters in Wisconsin were surveyed between 2002 and 2004. We found that fish species diversity decreased as agricultural land was replaced by urban land. In addition, tributary position within the drainage network caused significant differences in fish species diversity; specifically, we found significantly less fish species diversity in main-stem tributary streams located lower in the drainage network than in similarly sized streams located in the headwaters of the drainage area. Fish species composition, determined by multivariate principal components analysis, also showed significant differences among stream position within...

Studies regarding the thermal ecology of snakes are important to understanding their life histories. Yet, little is known about the thermal ecology of the North American genus Pituophis, which includes the bullsnake ( Pituophis catenifer sayi ). In an attempt to determine which independent variables significantly affected the thermal ecology of free-ranging bullsnakes, we tracked 12–19 radio-tagged individuals weekly from 2003 to 2005 in Wisconsin (USA) with temperature-sensitive transmitters. Although snake body temperature was found to vary based on several variables treated independently, two separate three-way interactions among variables were significant. We believe our results support the notion that P. c. sayi thermoconforms to environmental conditions in the upper Midwest, but more research on the topic is necessary.

In haplochromine cichlids, female mate choice based on male nuptial coloration has played an important role in speciation. Recent studies suggest that male coloration strongly influences the distribution of these fishes based on male–male aggression; males direct more aggression towards similarly coloured opponents while tolerating differently coloured individuals. We explored the role of male nuptial colour in aggression among the mbuna of Lake Malawi, examining aggression by male Metriaclima mbenjii , the red top cobalt zebra, towards conspecific opponents, similarly coloured heterospecific opponents and differently coloured heterospecifics. In trials in which focal males were offered a single opponent, while the total number of aggressive behaviours did not vary among opponent species, the types of behaviours did; focal males directed more lateral displays towards conspecifics than towards the other opponent species. When focal males were offered two opponents simultaneously, M. mbenjii directed more aggressive behaviours and more lateral displays towards similarly coloured opponents, regardless of species. Furthermore, when offered a conspecific and a similarly coloured opponent simultaneously, there were no differences in behaviour towards either opponent. Thus, nuptial coloration is used by males to identify competitors, and it suggests that male–male aggression may have also been an important diversifying force in speciation in rock-dwelling Lake Malawi cichlids.

Speciation via intersexual selection on male nuptial colour pattern is thought to have been a major force in promoting the explosive speciation of African haplochromine cichlids, yet there is very little direct empirical evidence of directional preferences within populations. In this study, we used objective spectrophotometry and analyses based on visual physiology to determine whether females of the Katale population of Labeotropheus fuelleborni, a Lake Malawi haplochromine, prefer males that have higher chroma and more within-pattern colour contrast. In paired male preference tests, female Katale L. fuelleborni showed increasing preferences for males with more relatively saturated colours on their flanks. They also showed increasing preferences for males with relatively higher contrast levels among flank elements. This is the first empirical evidence, to our knowledge, for male colour as a directionally sexually selected trait within a haplochromine cichlid population.