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The Neches River Rose Mallow (Hibiscus dasycalyx) is a rare wildflower endemic to Texas that is federally protected in the U.S.A. While previous work suggests that H. dasycalyx may be hybridizing with its widespread congeners, the Halberd-leaved Rose Mallow (H. laevis) and the Woolly Rose Mallow (H. moscheutos), this has not been studied in detail. We evaluated the relative threats to H. dasycalyx posed by hybridization with H. laevis and H. moscheutos by 1) examining their relatedness to one another via modern phylogenomic methods, 2) examining the species’ ecological (dis)similarities to one another using ecological niche modeling, and 3) looking for genomic evidence of hybridization among the three species. Our results suggest that H. dasycalyx is very closely related and ecologically similar to H. laevis, and suggest that H. laevis is interbreeding with H. dasycalyx in the wild. Conversely, H. moscheutos appears to be more distantly related to H. dasycalyx and more ecologically dissimilar, and the two are most likely not hybridizing. For these reasons, we believe that H. laevis poses a greater threat to H. dasycalyx than H. moscheutos. We offer some hypotheses as to why H. dasycalyx and H. laevis are coming into secondary contact where hybridization can occur.

Freshwater mussels in the family Unionidae are a diverse faunal group in North America. Anthropogenic disturbances have caused many unionid species to be listed as threatened, endangered, o...

Fish have an ecologically significant role in the life-history of unionid freshwater mussels, as the larvae of most species are obligate ectoparasites (glochidia) on fish hosts. Although this ecological interaction is vital to freshwater mussel conservation, there is a paucity of data on fish-host specificity for many species. A species-specific DNA barcoding dataset utilizing the mitochondrial NADH dehydrogenase subunit 1 (ND1) gene was used to identify 154 glochidia attached to wild fish collected from March through August of 2013 in the Sabine and Neches rivers in Texas, U.S.A. These data include the first report of potential hosts for two state-threatened species, Fusconaia askewi (Marsh, 1896) and Pleurobema riddellii (I. Lea, 1862), as well as potential hosts for Amblema plicata (Say, 1817), Obliquaria reflexa (Rafinesque, 1820), Plectomerus dombeyanus (Valenciennes, 1827), Potamilus purpuratus (Lamarck, 1819), Quadrula mortoni (I. Lea, 1831), Q. verrucosa (Rafinesque, 1820), and Truncilla truncata (Rafinesque, 1820). Cyprinella lutrensis appears to be the primary host for F. askewi, as 50% (54/108) of its glochidia were found on this minnow species alone. Pleurobema riddellii may be a cyprinid specialist, infesting only C. lutrensis and Pimephales vigilax. Alternatively, F. askewi may be a host generalist, as glochidia were found encysted on 17 fish species suggesting that host fish availability may not be an important factor contributing to observed population declines. The findings here will be instrumental in the future conservation of these species, through the translocation to correct habitat and developing successful propagation programs

Unionid freshwater mussels are one of the most imperilled groups in North America. They play an important role in freshwater ecosystems, both as a food source and as filter feeders. Their priority conservation status has generated interest in unionid research. Here, data from the US Geological Survey was used to produce predictive models of mussel habitat affinities at a resolution of 100 m2 across an area of thousands of square kilometres. This approach correctly identifies areas that are more suitable for threatened mussel species beds as compared with less suitable areas (>97% of the time) Stream segments were identified that are forecast to have high suitability for threatened mussels. Potamilus amphichaenus differed from other threatened mussel species by being associated with a wider range of volumetric flow rates and by not being restricted by the clay content of the soils. Of the species examined, it was the most large-river oriented in habitat use and distribution. These methods can help conservation planners and land-use managers make rational decisions about where to focus their efforts in lotic habitats without the need for intensive environmental measurements while still providing high-resolution information.

Freshwater mussel composition and abundance in stream ecosystems are influenced by changes in environmental and hydrologic forces related to stream size. Mussel assemblages in headwater areas tend to be depauperate but distinctive, with species richness and abundance increasing rapidly with increasing stream size. We compared the mussel assemblages in 3 subwatersheds of the Neches River Basin of east Texas: the small Attoyac Bayou (4th order), the intermediate-sized Angelina River (5th order), and the large mainstem of the upper Neches River (6th order). We conducted timed searches at 75 sites and found 12,860 mussels comprising 26 species. As in other river systems, the smallest stream segment, the Attoyac Bayou, had several species more adapted for low flow rates and stagnant conditions. The largest stream segment, the upper Neches River, had the highest diversity and abundance of unionids. We found that mussel abundances increased as the streamsegment size increased. In addition, we found a ch...

An expression in a functional programming language can be compiled into a massively redundant, spatially distributed, concurrent computation called a distributed virtual machine (DVM). A DVM is comprised of bytecodes reified as actors undergoing diffusion on a two-dimensional grid communicating via messages containing encapsulated virtual machine states (continuations). Because the semantics of expression evaluation are purely functional, DVMs can employ massive redundancy in the representation of the heap to help ensure that computations complete even when large areas of the physical host substrate have failed. Because they can be implemented as asynchronous circuits, DVMs also address the well known problem affecting traditional machine architectures implemented as integrated circuits, namely, clock networks consuming increasingly large fractions of area as device size increases. This paper describes the first hardware implementation of a DVM. This was accomplished by compiling a VHDL specification of a special purpose distributed memory multicomputer with a mesh interconnection network into a globally asynchronous, locally synchronous (GALS) circuit in an FPGA. Each independently clocked node combines a processor based on a virtual machine for compiled Scheme language programs, with just enough local memory to hold a single heap allocated object and a continuation.