Patrick J. Ciccotto

The ecological drivers of nuptial color evolution in darters (Percidae: Etheostomatinae).

Closely related animal lineages often vary in male coloration, and ecological selection is hypothesized to shape this variation. The role of ecological selection in inhibiting male color has been documented extensively at the population level, but relatively few studies have investigated the evolution of male coloration across a clade of closely related species. Darters are a diverse group of fishes that vary in the presence of elaborate male nuptial coloration, with some species exhibiting vivid color patterns and others mostly or entirely achromatic. We used phylogenetic logistic regression to test for correlations between the presence/absence of color traits across darter species and the ecological conditions in which these species occur. Environmental variables were correlated with the presence of nuptial color in darters with colorful species tending to inhabit environments that would support fewer predators and potentially transmit a broader spectrum of natural light compared to species lacking male coloration. We also tested the color preferences of a common darter predator, largemouth bass, and found that it exhibits a strong preference for red, providing further evidence of predation as a source of selection on color evolution in darters. Ecological selection therefore appears to be an important factor in dictating the presence or absence of male coloration in this group of fishes.

Dense Taxon Sampling Using AFLPs Leads to Greater Accuracy in Phylogeny Estimation and Classification of Darters (Percidae: Etheostomatinae)

The classification of the North American darters (Percidae: Etheostomatinae) has been a subject of historical interest and rigorous debate. Conflicting morphological and molecular phylogenetic analyses have made relationships among species unclear and have hampered attempts at classification. Recently we showed that amplified fragment length polymorphism (AFLP) data provide support for relatively ancient relationships (>30 mya) among darters that are consistent with numerous morphological hypotheses. We predicted that increasing the number of extant species sampled would result in a more accurate estimate of evolutionary relationships and increase the statistical resolution, particularly at deeper nodes, as it would increase the probability that two taxa share homologous alleles (fragments) and link deeper relationships, thus overcoming noise created by homoplasious fragments. To test this prediction, we added 32 species to our original analysis of 69 species and reconstructed evolutionary histories using Bayesian methods for AFLPs to infer phylogenetic relationships. Overall resolution of the tree substantially improved. Bayesian Posterior Probabilities were strong (greater than 0.95) at most of the deeper nodes, and most notably increased to 0.97 and 0.99 BPP at the two most ancient and previously weakly supported nodes in Etheostoma (estimated divergence approximately 26.1–33.5 mya). Our results indicated that dense taxon sampling may be necessary to increase accuracy and resolution when reconstructing ancient evolutionary relationships using AFLPs. Results of the present study were compared with earlier classifications and with recent studies on phylogenetic relationships to identify best-supported genera and subgenera.

Male Association Preference for Conspecifics in the Redband Darter, Etheostoma luteovinctum (Teleostei: Percidae) Based on Visual Cues

Divergent visual signals and associated mate preferences are frequently hypothesized to result in behavioral isolation between species lineages. Females are traditionally predicted to be the choosier sex, using visual cues such as male color to facilitate mate recognition and assessment. However, a number of authors have hypothesized that males also are selective in choosing mates and that male preferences can be important in maintaining behavioral isolation. Darters of the genus Etheostoma (Percidae) are a diverse group of sexually dimorphic fishes in which males of most species exhibit elaborate nuptial coloration during spawning seasons. Male coloration is hypothesized to play a role in maintaining behavioral isolation between darter species, and females show association preferences for conspecific male coloration. However, the degree to which males exhibit preferences for conspecific female visual cues is less clear. We examined conspecific association preferences based only on visual signals in male Redband Darter, Etheostoma luteovinctum. We presented individuals with a choice of a conspecific female or a female E. hopkinsi, a heterospecific that is almost completely behaviorally isolated from E. luteovinctum and differs in coloration and body shape. Males exhibited a statistically significant association preference for conspecifics in dichotomous choice trials where only visual cues were available. This is the first study to document a significant conspecific association preference in males of a darter species, providing evidence that males may contribute to behavioral isolation from E. hopkinsi. Differences in female coloration, body shape, or behavior appear to serve as important signals that would help maintain behavioral isolation between E. luteovinctum and E. hopkinsi upon secondary contact.

Preference for conspecifics evolves earlier in males than females in a sexually dimorphic radiation of fishes: MALE MATE CHOICE IN EARLY BEHAVIORAL ISOLATION

Speciation by sexual selection is generally modeled as the coevolution of female preferences and elaborate male ornaments leading to behavioral (sexual) reproductive isolation. One prediction of these models is that female preference for conspecific males should evolve earlier than male preference for conspecific females in sexually dimorphic species with male ornaments. We tested that prediction in darters, a diverse group of freshwater fishes with sexually dimorphic ornamentation. Focusing on the earliest stages of divergence, we tested preference for conspecific mates in males and females of seven closely related species pairs. Contrary to expectation, male preference for conspecific females was significantly greater than female preference for conspecific males. Males in four of the 14 species significantly preferred conspecific females; whereas, females in no species significantly preferred conspecific males. Relationships between the strength of preference for conspecifics and genetic distance revealed no difference in slope between males and females, but a significant difference in intercept, also suggesting that male preference evolves earlier than females’. Our results are consistent with other recent studies in darters and suggest that the coevolution of female preferences and male ornaments may not best explain the earliest stages of behavioral isolation in this lineage.

From 12 to One Species: Variation in Lobocheilos rhabdoura (Fowler, 1934) (Cyprinidae: Labeonini)

The cyprinid genus Lobocheilos in mainland Southeast Asia has a complex taxonomic history, with 12 nominal species described in the early- to mid-20th Century from Thailand, Laos, and Vietnam by several authors based primarily on lateral melanin pigmentation and morphometric data. More recent works tentatively recognize anywhere from two to six valid species in the region. The goal of this study was to examine morphological variation between these putative species to determine if they represent distinct species. Examinations of 445 specimens, including all available type material, from throughout the region failed to define morphologically distinct groups or any differences between allopatric populations in the major zoogeographic regions in the area. Furthermore, an ontogenetic pattern of lateral melanin pigmentation was identified that has likely contributed to taxonomic confusion. One species is recognized from this region, with the oldest available name being L. rhabdoura (Fowler, 1934). Lobocheilos rhabdoura is herein redescribed, and phylogenetic relationships of populations throughout the region are reconstructed.

Water Chemistry and Landscape Patterns in the Distribution of Banded Sunfish (Enneacanthus obesus) in Streams of the Atlantic Coastal Plain in Maryland

Abstract Water chemistry and landscape data were analyzed from streams in the Atlantic Coastal Plain physiographic province in Maryland, USA, to identify patterns in the spatial distribution of the state rare Banded Sunfish (Enneacanthus obesus). Principal component analysis was used to assess patterns in the distribution of this species based on select environmental variables. Mantel tests were conducted to further assess the correlation of environmental variables with the distribution of Banded Sunfish in Maryland while accounting for spatial autocorrelation. The distribution of Banded Sunfish was correlated with acidic stream segments with high concentrations of dissolved organic carbon and higher proportions of forest and wetland landscapes in upstream catchments. Conservation of Banded Sunfish will require the preservation of acidic, blackwater habitats through the protection of natural forest and wetland landscapes and limiting of the potentially harmful impacts of agricultural practices and urbanization. Such practices would likely benefit other native fishes throughout the region as well.

A new species of Lobocheilos (Teleostei: Cyprinidae) from East Kalimantan, Indonesian Borneo

Lobocheilos aurolineatus, new species, is described from the Mahakam River basin in East Kalimantan, Indonesian Borneo. It is distinguished from all other species of Lobocheilos except for L. ixocheilos and L. tenura in having one pair of barbels (maxillary) and by the presence of a broad, black midlateral stripe, approximately ¾ scale height in thickness, extending from the operculum to the caudal-peduncle base. Lobocheilos aurolineatus differs from both species in possessing a thin cream to yellow stripe on the anterior ⅔ of the flank, separating the black midlateral stripe from the brown dorso-lateral scales, and by a smaller mouth width (23.5-29.9% head length in L. aurolineatus vs. 32.1-45.0% and 34.4-46.4% head length in L. ixocheilos and L. tenura, respectively).

Papers on fishes of Asia, including those presented at international conferences of the Asian Society of Ichthyologists in Taipei, Taiwan in 2016, and in Ho Chi Minh City, Vietnam in 2017 (Cover & Copytight page)

(Cover Copytight page).

The evolution of male nuptial colour in a sexually dimorphic group of fishes (Percidae: Etheostomatinae)

To test hypotheses explaining variation in elaborate male colouration across closely related species groups, ancestral-state reconstructions and tests of phylogenetic signal and correlated evolution were used to examine the evolution of male body and fin colouration in a group of sexually dichromatic stream fishes known as darters (Percidae: Etheostomatinae). The presence or absence of red-orange and blue-green male colour traits were scored across six body regions in 99 darter species using a recently estimated amplified fragment length polymorphism (AFLP) phylogeny for comparative analyses. Ancestral-state reconstructions infer the most recent common ancestor of darters to lack red-orange colour and possess blue-green colour on different body regions, suggesting variation between species is due to independent gains of red-orange and losses of blue-green. Colour traits exhibit substantial phylogenetic signal and are highly correlated across body regions. Comparative analyses were repeated using an alternative phylogenetic hypothesis based on one mitochondrial and two nuclear genes, yielding similar results to analyses based on the AFLP phylogeny. Red-orange colouration in darters appears to be derived; whereas, blue-green appears to be ancestral, which suggests that different selection mechanisms may be acting on these two colour classes in darters.

Revision of the Cyprinid Genus Crossocheilus (Tribe Labeonini) with Description of a New Species

The Southeast Asian cyprinid genus Crossocheilus was briefly described by Kuhl and van Hasselt in 1823 and, despite the short description, has remained a valid genus. However, the genus and its species are frequently misidentified in institutional collections, likely due to the absence of a detailed diagnosis and description, as well as the superficial morphological similarity with other cyprinid genera in the region. Crossocheilus and its constituent species are herein revised based on an examination of morphology and pigmentation. Eleven species are recognized, including a new species described from Indonesia. Crossocheilus pseudobagroidesis a junior synonym of C. langei. Crossocheilus tchangi is removed from synonymy with C. reticulatus and is a senior synonym of C. stigmaeus. Phylogenetic relationships among species of Crossocheilus based on sequences from the nuclear encoded recombination activating gene 1 are reconstructed. The resultant phylogeny is the most taxonomically comprehensive estimation of relationships among Crossocheilus to date and resolves C. atrilimes and C. oblongus, previously hypothesized to be sister species, not to be most closely related to one another.