William D. Pearson

Doomed before they are described? The need for conservation assessments of cryptic species complexes using an amblyopsid cavefish (Amblyopsidae: Typhlichthys) as a case study

The delimitation of cryptic species and lineages is a common finding of phylogenetic studies. Species previously considered to be of low conservation priority might actually be comprised of multiple lineages with substantially smaller geographic ranges and smaller populations that are of much greater conservation concern and that require different conservation strategies. Cryptic biodiversity is an especially common finding in phylogenetic studies of subterranean fauna; however, most cryptic lineages remain undescribed and have not been subjected to conservation assessments. As many subterranean species are of high conservation concern, the conservation assessment of cryptic lineages is important for developing effective conservation and management strategies. In particular, some lineages might be in need of immediate conservation action even before formal taxonomic description. Here we explore this issue by conducting IUCN Red List and NatureServe conservation assessments on recently discovered cryptic lineages of the southern cavefish (Typhlichthys subterraneus) species complex. We ascertained threats associated with extinction risk, identified priority lineages and populations for immediate conservation efforts, and identified knowledge gaps to expedite the development of conservation and management strategies before formal taxonomic description. Most cryptic lineages are at an elevated risk of extinction, including one lineage classified as “Critically Endangered.” We identified ten threats impacting cavefish lineages that vary in both scope and severity, including groundwater pollution, hydrological changes from impoundments, and over-collection. Our threat assessments and recommendations can be used by stakeholders to prioritize effective and appropriate management initiatives aiding in the conservation of these lineages even before they are formally recognized.

Effects of climatic and geological processes during the pleistocene on the evolutionary history of the northern cavefish, Amblyopsis spelaea (teleostei: amblyopsidae).

Climatic and geological processes associated with glaciation cycles during the Pleistocene have been implicated in influencing patterns of genetic variation and promoting speciation of temperate flora and fauna. However, determining the factors promoting divergence and speciation is often difficult in many groups because of our limited understanding of potential vicariant barriers and connectivity between populations. Pleistocene glacial cycles are thought to have significantly influenced the distribution and diversity of subterranean invertebrates; however, impacts on subterranean aquatic vertebrates are less clear. We employed several hypothesis‐driven approaches to assess the impacts of Pleistocene climatic and geological changes on the Northern Cavefish, Amblyopsis spelaea, whose current distribution occurs near the southern extent of glacial advances in North America. Our results show that the modern Ohio River has been a significant barrier to dispersal and is correlated with patterns of genetic divergence. We infer that populations were isolated in two refugia located north and south of the Ohio River during the most recent two glacial cycles with evidence of demographic expansion in the northern isolate. Finally, we conclude that climatic and geological processes have resulted in the formation of cryptic forms and advocate recognition of two distinct phylogenetic lineages currently recognized as A. spelaea.

Production and energy flow in the benthic community of a Texas pond

Energy flow (A = R + P; assimilation = respiration + production) and life-history/density-biomass cycles were followed for 1 year in a mayfly (Brachycercus sp.) population and two chironomid (Procladius sp. and Tendipes decorus) populations in a 0.94 ha pond located in north-central Texas. Temperature (5, 10, 15, 20, 25 and 30°C) effects on R and patterns of metabolic compensation/acclimatization were determined for the mayfly and chironomids. Chironomid and mayfly populations dominated the nine benthic macroinvertebrates identified in the pond, with greatest abundances in winter and winter-spring respectively. Annual energy flow was 51 kcal m−2 (R = 40 kcal, P = 11 kcal or 1.9 g) in Brachycercus sp., 23 kcal m−2 (R = 5 kcal, P = 18 kcal or 2.4 g) in Procladius sp. and 74 kcal m−2 (R = 17 kcal, P = 57 kcal or 6.0 g) in T. decorus. Each species metabolically compensated partially to temperatures en countered during their life histories.

Reservoir Ranching of Paddlefish

Abstract Paddlefish Polyodon spathula (30–67 cm total length, TL) were stocked in six flood control reservoirs (<41 ha) in western Kentucky in January 1995 at a target stocking density of 10 fish/ha. Fish growth was monitored quarterly beginning in July 1995. The fish were implanted intraperitoneally with passive integrated transponder (PIT) tags. Chemical and physical variables and zooplankton biomass were measured monthly. Three reservoirs that had not been stocked were sampled monthly as controls. Of the 1,440 paddlefish stocked, 353 were recovered at harvest in the fall of 1996, and only two tags were found. Anecdotal evidence indicated some loss to predation by largemouth bass Micropterus salmoides and some to escapes through mechanical spillways. The total gross yield was 1,715 kg or 13.7 kg/ha; it ranged from 0.6 to 28.8 kg/ha. Gill nets of 102-mm-bar mesh were optimum for harvest. Mean harvest weights were significantly different among reservoirs. A positive correlation was found between relative ...

Phytoplankton dynamics, primary productivity and community metabolism in a north-central Texas pond

AbstractPhytoplankton diversity, primary productivity and community metabolism were measured for 1 year in a 0.94 ha pond located in north-central Texas. Gross primary production ranged from 4.5 to 46.8 kcal m−2 day−1 (

Acclimation temperature and temperature tolerance in fingerling largemouth bass (Micropterus salmoides)

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Rose Bengal Stain as an Aid in Sorting Larval Fish Samples

=22.0 kcal m−2 day−1) and community metabolism ranged from 7.3 to 32.4 kcal m−2 day−1 (