Kyle R. Piller

DO FRESHWATER FISHES DIVERSIFY FASTER THAN MARINE FISHES? A TEST USING STATE‐DEPENDENT DIVERSIFICATION ANALYSES AND MOLECULAR PHYLOGENETICS OF NEW WORLD SILVERSIDES (ATHERINOPSIDAE)

Freshwater habitats make up only ∼0.01% of available aquatic habitat and yet harbor 40% of all fish species, whereas marine habitats comprise >99% of available aquatic habitat and have only 60% of fish species. One possible explanation for this pattern is that diversification rates are higher in freshwater habitats than in marine habitats. We investigated diversification in marine and freshwater lineages in the New World silverside fish clade Menidiinae (Teleostei, Atherinopsidae). Using a time‐calibrated phylogeny and a state‐dependent speciation–extinction framework, we determined the frequency and timing of habitat transitions in Menidiinae and tested for differences in diversification parameters between marine and freshwater lineages. We found that Menidiinae is an ancestrally marine lineage that independently colonized freshwater habitats four times followed by three reversals to the marine environment. Our state‐dependent diversification analyses showed that freshwater lineages have higher speciation and extinction rates than marine lineages. Net diversification rates were higher (but not significant) in freshwater than marine environments. The marine lineage‐through time (LTT) plot shows constant accumulation, suggesting that ecological limits to clade growth have not slowed diversification in marine lineages. Freshwater lineages exhibited an upturn near the recent in their LTT plot, which is consistent with our estimates of high background extinction rates.

Systematics and Biogeography of the Silverside Tribe Menidiini (Teleostomi: Atherinopsidae) Based on the Mitochondrial ND2 Gene

Abstract The silverside fish tribe Menidiini (Teleostei: Atherinopsidae) consists of four genera, Menidia, Labidesthes, Poblana, and Chirostoma, that are distributed along the Atlantic coast of North America, throughout the Gulf of México, insular United States, and the Mesa Central of México. It has been suggested that Chirostoma, Poblana, and Menidia should be recognized as a single genus under the nominal Menidia. To test this hypothesis, phylogenetic relationships within the tribe Menidiini were assessed using the mitochondrially encoded ND2 gene. Monophyly of the Menidiini tribe was supported. Results also failed to support monophyly for the genera Menidia and Chirostoma as currently recognized. A central Mexican clade, inclusive of Chirostoma and Poblana, was recovered as monophyletic and strongly supported. Relationships within the Mesa Central clade support a previously recognized “humboldtianum” clade and the paraphyly of Chirostoma with respect to Poblana.

Multi-locus fossil-calibrated phylogeny of Atheriniformes (Teleostei, Ovalentaria)

Phylogenetic relationships among families within the order Atheriniformes have been difficult to resolve on the basis of morphological evidence. Molecular studies so far have been fragmentary and based on a small number taxa and loci. In this study, we provide a new phylogenetic hypothesis based on sequence data collected for eight molecular markers for a representative sample of 103 atheriniform species, covering 2/3 of the genera in this order. The phylogeny is calibrated with six carefully chosen fossil taxa to provide an explicit timeframe for the diversification of this group. Our results support the subdivision of Atheriniformes into two suborders (Atherinopsoidei and Atherinoidei), the nesting of Notocheirinae within Atherinopsidae, and the monophyly of tribe Menidiini, among others. We propose taxonomic changes for Atherinopsoidei, but a few weakly supported nodes in our phylogeny suggests that further study is necessary to support a revised taxonomy of Atherinoidei. The time-calibrated phylogeny was used to infer ancestral habitat reconstructions to explain the current distribution of marine and freshwater taxa. Based on these results, the current distribution of Atheriniformes is likely due to widespread marine dispersal along the margins of continents, infrequent trans-oceanic dispersal, and repeated invasion of freshwater habitats. This conclusion is supported by post-Gondwanan divergence times among families within the order, and a high probability of a marine ancestral habitat.

Molecular systematics of the enigmatic Middle American genus Vieja (Teleostei: Cichlidae).

The genus Vieja represents a group of heroine cichlids (Teleostei: Cichlidae) distributed on the Atlantic and Pacific slopes of North and Central America from southern Mexico to Panama. Sixteen species of Vieja are presently recognized; however, based on long-standing taxonomic problems, the genus itself appears to be weakly defined. A number of different generic designations have been proposed for members of Vieja, and recent systematic studies of heroine cichlids have not specifically addressed the validity of the grouping and have not included all species in the genus. Therefore, the purpose of this study was to assess the monophyly of the genus Vieja by including all nominal species in the genus using the mitochondrial encoded cytochrome b gene and nuclear S7-1 intron. Results of Maximum Parsimony, Bayesian inference, and topology tests (constraint tree searches and post-burn-in Bayesian filtering) indicate that the genus is not monophyletic as it is currently recognized. The genus Herichthys was recovered as sister to a clade consisting of a number of Vieja species (V. fenestrata, V. guttulata, V. zonata, V. hartwegi, V. bifasciata, V. breidohri, V. argentea, V. regani, V. melanura, V. synspila, and V. maculicauda, as well as Paraneetroplusbulleri). A clade consisting of V. intermedia, V. godmanni, and V. microphthalma was recovered sister to Theraps. Additionally, V. heterospila and V. tuyrensis were recovered outside of Vieja and Herichthys clades. Based on the results of this comprehensive study, we suggest a revised classification of Vieja species.

It's a family matter: molecular phylogenetics of Atheriniformes and the polyphyly of the surf silversides (family: Notocheiridae).

Phylogenetic relationships among families of Atheriniformes have long been problematic. The affinities of one of the most enigmatic lineages, surf silversides (Notocheiridae), have proven particularly elusive due to this taxons unique morphology and rarity in museum collections. In this study, we use mitochondrial and nuclear sequence data to generate a phylogeny for seven of the eight families of Atheriniformes. Our results reveal that four families within Atheriniformes (Atherinopsidae, Notocheiridae, Atherinidae, Melanotaeniidae) are not monophyletic. Most notably, Notocheiridae is polyphyletic, with Notocheirus hubbsi nested within New World silversides (Atherinopsidae), while members of Iso are sister to all other Old World Atheriniforms. These data suggest that the unique morphology of Notocheirus and Iso is a result of adaptive convergent evolution to the high-energy surf habitat where these species live.

Morphological Variation of the Redfin Darter, Etheostoma whipplei, with Comments on the Status of the Subspecific Populations

Abstract The redfin darter, Etheostoma whipplei (Percidae: subgenus Oligocephalus) has been the subject of several taxonomic treatments over the past 50 years. At the present, two subspecies are recognized: Etheostoma whipplei whipplei in the Ozark and Ouachita Highlands and Etheostoma whipplei artesiae on the Gulf Coastal Plain. We examined variation in meristics and pigmentation to assess the distinctiveness of eastern populations of E. w. artesiae. The results indicated that E. w. artesiae differs significantly from E. w. whipplei in meristics and features of male breeding pigmentation. We conclude that all populations currently recognized as E. w. artesiae should be elevated to full species status.

Incomplete sampling, outgroups, and phylogenetic inaccuracy: A case study of the Greenside Darter complex (Percidae: Etheostoma blennioides)

The freshwater fish fauna of eastern North America is remarkable for its high species diversity (Mayden, 1992; Etnier and Starnes, 1993; Boschung and Mayden, 2004). One of the most diverse and well studied groups of freshwater fishes in this region are the darters (Teleostei: Percidae), which continue to be of high interest to evolutionary biologists and ecologists alike (Page, 1983; Bart and Page, 1992; Near, 2002). The greenside darter, Etheostoma blennioides, is one of the most widely distributed species of Etheostomatine darters (Lee et al., 1980). Morphological variation within the complex has attracted much taxonomic interest and has resulted in the description of many species now considered synonymous with E. blennioides (Miller, 1968). A comprehensive analysis of morphological variation within the complex was conducted by Miller (1968), who recognized four subspecies (blennioides, newmanii, gutselli, and pholidotum), several morphological races, and three zones of morphological intergradation. Variation within the complex has also attracted the interest of molecular systematists, resulting in two similar phylogeographic studies recently published in this journal (Piller et al., 2008; Haponski and Stepien, 2008). Piller et al. (2008) examined molecular variation in the mitochondrial cytochrome b gene, using data from 44 populations. Variation in the nuclear encoded S7 intron-1 was also examined for a subset of the specimens used in this study (N = 24). Multiple genetically distinctive clades were recovered, suggesting that there is more taxonomic diversity within the E. blennioides complex than is currently recognized (Piller et al., 2008). Haponski and Stepien (2008) examined variation in the same genetic markers for a larger number of individuals (N = 345), but fewer populations (N = 19). Conclusions of the two studies differed significantly. Here, we compare and contrast methodologies, analytical approaches, and con-

Black liquor and the hangover effect: fish assemblage recovery dynamics following a pulse disturbance

Anthropogenic perturbations impact aquatic systems causing wide-ranging responses, from assemblage restructuring to assemblage recovery. Previous studies indicate the duration and intensity of disturbances play a role in the dynamics of assemblage recovery. In August 2011, the Pearl River, United States, was subjected to a weak black liquor spill from a paper mill which resulted in substantial loss of fish in a large stretch of the main channel. We quantified resilience and recovery of fish assemblage structure in the impacted area following the event. We compared downstream (impacted) assemblages to upstream (unimpacted) assemblages to determine initial impacts on structure. Additionally, we incorporated historic fish collections (1988–2011) to examine impacts on assemblage structure across broad temporal scales. Based on NMDS, upstream and downstream sites generally showed similar assemblage structure across sample periods with the exception of the 2 months postdischarge, where upstream and downstream sites visually differed. Multivariate analysis of variance (PERMANOVA) indicated significant seasonal variation among samples, but found no significant interaction between impacted and unimpacted assemblages following the discharge event. However, multivariate dispersion (MVDISP) showed greater variance among assemblage structure following the discharge event. These results suggest that 2 months following the disturbance represent a time period of stochasticity in regard to assemblage structure dynamics, and this was followed by rapid recovery. We term this dynamic the “hangover effect” as it represents the time frame from the cessation of the perturbation to the assemblages return to predisturbance conditions. The availability and proximity of tributaries and upstream refugia, which were not affected by the disturbance, as well as the rapid recovery of abiotic parameters likely played a substantial role in assemblage recovery. This study not only demonstrates rapid recovery in an aquatic system, but further demonstrates the value of continuous, long-term, data collections which enhance our understanding of assemblage dynamics.

Salinity and Egg Shape Variation: A Geometric Morphometric Analysis

Abstract The harvest and incubation of American Alligator (Alligator mississippiensis) eggs is an important component to the commercial alligator harvest industry in the southeastern United States. As a result, various methodologies have been used to monitor alligator populations including abundance counts, stress quantification, and nesting surveys. Past studies have dismissed the importance of egg shape in crocodilians, Squamates, and turtles and deemed egg shape in birds and other amniotes as similar, in relation to functionality. The complexity of crocodilian eggs has been examined, and both turtle and Squamate eggs have been regarded recently as physiologically more intricate than bird eggs. This study introduces a physiological approach to monitor alligator populations in freshwater and low salinity environments by quantifying egg shape in correlation with varying salinity. We introduce a fractional semilandmark-shape template method to quantify egg shape within a geometric morphometric framework. This approach is beneficial because it allows for the quantification of shape for curved structures, such as eggs, which lack homologous landmarks. The results from this study suggest that alligator egg shape is correlated with varying salinity levels, such that variation in alligator egg shape at low salinities changes in gradient-like fashion, whereas salinities high enough to be deemed stressful result in reversion back to a low salinity egg shape or desiccation. This study elucidates a correlation that can be implemented in management and breeding techniques and opens the door to in-depth physiological examination of the system.

Two New Intergeneric Hybrids Involving Semotilus atromaculatus and the Genus Phoxinus with Analysis of Additional Semotilus atromaculatus: Phoxinus Hybrids

Natural hybridization is relatively common among North American cyprinids (Schwartz, 1972, 1981), especially among species that spawn over the gravel nests of pit-, pit-ridge-, and mound-building cyprinids (Johnston and Page, 1992). A widespread pit-ridge-building cyprinid, the creek chub, Semotilus atromaculatus, is known to hybridize with a number of cyprinids (Schwartz, 1972, 1981). There are numerous reports of hybrids involving species of Phoxinus, including P oreas (Hambrick, 1977; Maurakis and Woolcott, 1992), P erythrogaster (Cross and Minckley, 1960; Greenfield et al., 1973; Grady and Cashner, 1988), and P eos and P neogaeus (New, 1962; Legendre, 1970). There are no previous reports, however, of a hybrid involving two recently described species, the Tennessee dace, P tennesseensis, or the blackside dace, P cumberlandensis.