Abstract The variable platyfish (Xiphophorus variatus), native to Gulf Coast drainages of northern Mexico, is a popular aquarium fish with a long history of introduction globally. We document the first Texas occurrence of this species, and its persistence in highly urban Waller Creek in the city of Austin since at least 2004. The population appears to be limited to Waller Creek, having not yet been found in neighboring creeks where similar habitat exists. We observed individuals in situ and in the lab surviving in 7°C water, well below published thermal minima, and report its persistence through one of the coldest winters in Austin's recorded history. Its persistence may be due to a combination of its cold tolerance and the presence of thermal refuges. In the lab we found that individuals purchased in a local pet store and individuals from Waller Creek had the same cold tolerance. , Resumen El pez espada de Valles (Xiphophorus variatus), nativo de las cuencas afluentes del golfo de México del norte de México, es una especie popular de acuario con una historia larga de introducciones globales. Aquí documentamos la primera ocurrencia de la especie en Texas y su persistencia en un arroyo urbano, Waller Creek en la ciudad de Austin, a partir de por lo menos 2004. La población parece limitada a Waller Creek porque aún no se ha encontrado en arroyos cercanos con hábitat similar. Observamos individuos in situ y en el laboratorio sobreviviendo en agua de 7°C, mucho más frio que la mínima tolerancia termal publicada, y reportamos su persistencia a través de uno de los inviernos más fríos en la historia de Austin. Su persistencia puede ser atribuida a una combinación de su tolerancia al frío y existencia de refugios termales. En el laboratorio, individuos comprados en una tienda local de acuario e individuos de Waller Creek mostraron la misma tolerancia al frío.
Since Barbour proposed sympatric speciation to explain evolutionof silversides in the Lerma-Santiago basin, relatively little subsequent
study has been done. We assessed foraging patterns of four
sympatric silversides species (Chirostoma estor, Chirostoma grandocule,
Chirostoma attenuatum and Chirostoma patzcuaro) in Lago de
Pátzcuaro to understand resource partitioning and their sympatric
coexistence. We assessed the abundance of invertebrate prey in three
feeding habitats and measured physical and chemical habitat parameters
at two study sites. Fish were collected during the wet (September
1987) and dry (March 1988) seasons; a total of 242 gut contents were
analyzed. We evaluated the trophic guild of each species using the index
of relative importance (IRI), prey selectivity with the Ivlev Electivity
Index (E), dietary diversity using Shannon and Wiener diversity index
(H’), and diet overlap using Morisita index. All silverside species were
determined to be predaceous carnivores that feed mainly on nekton
and periphyton. Dietary diversity and prey selectivity patterns were
similar among species and diet overlap was >70%. Our data do not
support the proposition that coexistence of these four fish species is
maintained by dietary specialization. We hypothesize that sympatric
coexistence of atherinopsids in Lago de Pátzcuaro is explained by
food resource availability and ontogenetic variation in their diets. This
study highlights the importance of analyzing ecological patterns and
mechanisms as basic elements for designing conservation strategies of
species flocks, especially under habitat loss and introduction of exotic
species. Conservation efforts are urgent to preserve the rare evolutionary
process of sympatric speciation (habitat segregation) that is occurring
in other lakes in central Mexico, and probably already lost in the
Lago de Pátzcuaro, as a result of poor management and inadequate
Strategic conservation planning for broad, multi-species landscapes benefits from a data-driven approach that emphasizes persistence of all priority species populations and utilized landscapes, while simultaneously accounting for human uses. This study presents such an assessment for priority fishes of the Great Plains of the United States. Species distribution models for 28 priority fishes were created and incorporated into a prioritization framework using the open source software Zonation, accounting for species-specific connectivity needs and current fish habitat condition. Multiple additional assessments were then produced that i.) identify distinct species management units based on distance and compositional similarity of stream segments containing priority species, ii.) compare results of ranking species' conservation values at the local (state) and global scale, and iii.) provide 'bang-for-buck' perspectives, emphasizing richness of priority species, at state and major basin scales. Together, these analyses are intended to aid managers in effective allocation of conservation action with regards to imperiled fishes of the Great Plains. Implementation of a broad-scale multi-species approach such as this complements traditional reactive management and restoration by encouraging cooperation and coordination among stakeholders and partners, increasing efficiency of future monitoring and management efforts.
The desert, its resources and researchers! The two intersected for the 6th time as the Chihuahuan Desert Research Institute hosted over 200 participants for the symposium held at Sul Ross State University, 14th-17th of October 2004. The cumulative years of research experience, knowledge, and publications among participants was truly impressive, and all tied together at the conference by their individual care for, and research interest in, the natural resources of the Chihuahuan Desert region. By its bi-national nature, the conference represents a broad focus on the rich and complex biodiversity, ecosystems, and biogeography of the Chihuahuan Desert, with even greater representation at the conference (topics, titles, and authors) of the northern portion of the desert in northern México and the southwestern United States of America. As at the previous five conferences, the topics were diverse.The human dimension in the desert (uses, impacts, influences, and appreciation) was included and this time, a major synthetic overview of ecoregional planning and assessment of conservation concerns, values (species, natural communities, and ecosystems), specific sites, and predominant threats throughout the entire Chihuahuan Desert (click here for a complete copy of the Ecoregional Conservation Assessment for the Chihuahuan Desert).The potency of such a convention is of course, much more than just the excellent and professional presentation of papers and posters. It is also the hallway and after-hours conversations, exchanges of ideas and recollections, reunions and introductions. This conference covered a depth and breadth that has become the hallmark of the conference by reputation and inclusiveness. The range of topical sessions spanned from species-specific papers and sessions; to focus on specific conservation sites; to groupings like the desert herpetofauna and mammals; to sessions about aquatics, cacti, and exotic species; to ecosystems; and then the composite Chihuahuan Desert conservation overview.
The conference was launched by Chihuahuan Desert Research Institute Executive Director Cathryn Hoyt’s conference welcome, which was followed by the plenary Keynote Address given by Dr. Dean Hendrickson of the University of Texas at Austin. He set the tone for the conference with a sterling conservation message and alarm for one of the desert’s most notable biodiversity treasures—Cuatro Cienégas, Coahuila. His presentation looked at the history and future of Cuatro Cienégas and the effects of regional problems that are catching up in this time-lagged gem of the Chihuahuan Desert.
The threads and themes of the individual presentations and topical sessions also spanned the geography and topography of the northern Chihuahuan Desert. The basin-and-range physiography was covered from the grasslands of the basins to the forested sky island mountain ranges. Water is the most crucial and vital (and certainly limited and limiting) resource of the desert, hence the topical foci on aquatic resources from rare fishes and turtles to invertebrates and limnology in several sessions. There were topical sessions such as a panel presentation and group discussion on exotic species including salt cedar (Tamarix) and riparian restoration along the Rio Grande/ Rio Bravo, and a separate session just on exotic animals that threaten species, habitats, and natural communities, and which warrant concern and management.
This conference took on a markedly different angle from previous conferences in that there was considerable focus on landscape ecology, systems, and processes. An elaborate and sequentially-presented multi-session topic led by the Jornada Experimental Station research team covered landscape linkages and cross-scale interactions in the northern Chihuahuan Desert rangeland context; tying together soils, hydrology, and ecological management of complex ecological drivers within highly dynamic systems. Five full sessions were structured with a particular emphasis on semiarid grasslands specifically, with three on grassland vegetation ecology and restoration, another covering ecology of semiarid grassland mammals, and yet another devoted to semiarid grassland birds. One session included fire effects and ecological ramifications, trajectories, and outcomes of fire in the desert and mountains.
Finally, a full session was dedicated to natural resource interpretation and informal education within and about the desert. Topics included interpretation from a national park perspective; interpretation as a conservation tool; the importance of place and familiarity with an ecoregion; bioregional education; field schools, and backyard habitats. The unifying theme was tying the natural resources of the desert to the people who use, visit, reside within, conduct research, recreate, or merely appreciate the desert and wanting to know it better, and fuller. To this end, there was a special multi-day workshop on interpretive guide training and certification offered in conjunction with the Symposium. Held prior to the actual symposium, and hosted by the Chihuahuan Desert Research Institute in association with the National Association for Interpretation (the umbrella organization of natural and cultural resource interpretation), the program was facilitated and led by a professional interpretive trainer as a hands-on field school at nearby Camp Mitre Peak. Scholarships for attendees were generously provided by the Rio Grande Institute.
An additional rangeland health workshop was conducted following the Symposium. The workshop was titled “Interpreting Indicators of Rangeland Health: an Introduction to the Qualitative Rangeland Assessment Protocol” led by scientists from the USDA/ARS Jornada Experimental Range.
Sul Ross State University’s Museum of the Big Bend featured an exhibit developed in conjunction with the conference that opened as the conference began titled “Boundaries to Blair: Eight Scientists in the Big Bend.” The display included books and archival materials that highlighted the biological investigations and scientists of the borderlands from the early days of settlement up to the baseline-establishing biotic province surveys of W. Frank Blair, a University of Texas zoologist who was a keen early supporter of CDRI in its formative years.
The conference truly had at least bi-national representation with a registration of approximately 200 people. Just as significantly, the total number of presenters of technical presentations included 90 papers (by a cumulative 256 authors or coauthors) and 16 posters by 46 authors or coauthors. There were 26 moderated sessions, with student award competitions for the best paper presented from among 17 student competitors and for the best student poster.