Recent literature reviews of bioassessment methods raise questions about use of least-impacted reference sites to characterize natural conditions that no longer exist within contemporary landscapes. We explore an alternate approach for bioassessment that uses species site occupancy data from museum archives as input for species distribution models (SDMs) stacked to predict species assemblages of freshwater fishes in Texas. When data for estimating reference conditions are lacking, deviation between richness of contemporary versus modeled species assemblages could provide a means to infer relative biological integrity at appropriate spatial scales. We constructed SDMs for 100 freshwater fish species to compare predicted species assemblages to data on contemporary assemblages acquired by 4 independent surveys that sampled 269 sites. We then compared site-specific observed/predicted ratios of the number of species at sites to scores from a multimetric index of biotic integrity (IBI). Predicted numbers of species were moderately to strongly correlate with the numbers observed by the four surveys. We found significant, though weak, relationships between observed/predicted ratios and IBI scores. SDM-based assessments identified patterns of local assemblage change that were congruent with IBI inferences, however, modeling artifacts that likely contributed to over-prediction of species presence may restrict the stand-alone use of SDM-derived patterns for bioassessment and therefore warrant examination. Our results suggest that when extensive standardized survey data that includes reference sites are lacking, as is commonly the case, SDMs derived from generally much more readily available species site occupancy data could be used to provide a complementary tool for bioassessment.
Fishes of the family Salmonidae, including trout (Oncorhynchus), charr (Salvelinus), salmon (Oncorhynchus and Salmo), grayling (Thymallus) and whitefish (Prosopium), are expected to be particularly vulnerable to climate change because of their dependence on cold, clean water. Salmonids are among the most sought after fish by recreational anglers. In North America, their native range includes much of the continent from the Arctic Plains, along Pacific and Atlantic coasts, and throughout most mountainous regions (Behnke 2002). In Mexico, trout naturally occur in the mountainous regions of Baja California, and throughout the Sierra Madre Occidental as far south as the Rio Presidio and Rio Baluarte basins (Hendrickson et al. 2002). Brown trout (Salmo trutta) are native to Europe but have been broadly introduced in North America. Additionally, rainbow trout (O. mykiss) and brook trout (Salvelinus fontinalis) and other salmonids that are native to North America have been widely introduced into lakes, reservoirs, and river systems outside of their native ranges to increase angling opportunities.Climate change is likely to continue affecting salmonids throughout their ranges. Increasing air temperatures have been warming stream and lake temperatures (Schneider and Hook 2010; Asaak et al. 2012) with impacts ranging from growing stress and metabolic rates to loss of lower elevation habitats as waters warm (Eby et al. 2014; Keefer and Caudill 2015). Warmer conditions will also impact salmonids through changes in winter precipitation and altered flow regimes (Haak et al. 2010). Disturbance events, such as wildfires, floods, and drought, are likely to increase as well (Westerling et al. 2006) with resulting stream sedimentation (Goode et al. 2012). Many existing stressors for salmonids are likely to be made worse by climate change (Williams et al. 2015). For instance, non-native fishes, which now prey on and compete with native salmonids, are likely to increase in numbers and distributions as climate changes (Rahel and Olden 2008; Lawrence et al. 2014). The synergies that emerge from the combined effects of these stressors will be hard to predict with accuracy but are likely to magnify the negative consequences of climate change for coldwater fishes in North America.
The range of climate change impacts will not be equally harmful across all salmonid species. Although, all salmonids tend to be dependent on cold, clean water supplies, some species, such as bull trout (Salvelinus confluentus), Arctic grayling (Thymallus arcticus), and Dolly Varden (S. malma), are particularly sensitive to increasing temperatures and sedimentation (Selong et al. 2001; Jones et al. 2013). Changes in winter precipitation from snow to rain may impact fall-spawning species such as brook trout or brown trout to a greater degree than spring-spawning trout because of increased scouring of their egg beds (Wenger et al. 2011; Goode et al. 2013). Other species, such as California golden trout (O. aquabonita) and Lahontan cutthroat trout (O. clarkii henshawi), may occur in regions that are in the midst of sustained drought and particularly vulnerable to loss because of increasing isolation and small population size.
Despite our understanding of climate-driven impacts and known sensitivity of salmonids to warming conditions, predictions of future ecological conditions are complicated by the interactions among climate, biological, and geological processes. None of these factors act in isolation. The degree that warming and changes in disturbances impact particular habitats and species depends on the resilience of the habitat or species in question, including the interactions of biological, geomorphic and hydrologic systems. Impacts from climate change are likely to be more severe where stream and lake conditions are degraded or fragmented and less severe where habitats are robust and interconnected (Rieman and Isaak 2010). Unfortunately, many habitats of native salmonids have a legacy of pollution and fragmentation caused by dams, water diversions, agricultural runoff, and roads. The majority of native trout and charr species and subspecies occupy less than 25% of their historical habitat (Trout Unlimited 2015).
The purposes of this paper are to 1) review existing and likely future climate change impacts to salmonids in North America, 2) provide a primary bibliography for these impacts, and 3) describe how restoration can help trout adapt to climate change. The reader should keep in mind that the conservation status of most native salmonids already has declined as a result of the legacy of agricultural development, hydropower development, and the introduction of non-native species (Behnke 2002; Trout Unlimited 2015). Some taxa already are classified as vulnerable, threatened, or endangered by state, provincial, and federal agencies. Furthermore, as occupied habitat becomes increasingly fragmented and isolated, risks to climate-driven disturbances increase as well. Conservation efforts such as building artificial barriers to protect native trout from upstream invasions of non-native trout and warmwater fishes may result in further vulnerability to climate change because of range restrictions. Thus it is important to view increasing risk not just from the perspective of one or two factors but from the full variety of impacts that may accumulate over space and time.
Behavioral studies have often examined parental care by measuring phenotypic plasticity of behavior within a species. Phylogenetic studies have compared parental care among species, but only at broad categories (e.g., care vs. no care). Here we provide a detailed account that integrates phylogenetic analysis with quantitative behavioral data to better understand parental care behavior in the Cuatro Ciénegas cichlid, Herichthys minckleyi. We found that H. minckleyi occurs in a clade of sexually monochromatic or weakly dichromatic monogamous species, but that male and female H. minckleyi have dramatically different reproductive coloration patterns, likely as a result of sexual selection. Furthermore, we found that males are polygynous; large males guard large territories, and smaller males may attempt alternative mating tactics (sneaking). Finally, compared to the closely related monogamous Rio Grande cichlid, H. cyanoguttatus, males of H. minckleyi were present at their nests less often and performed lower rates of aggressive offspring defense, and females compensated for the absence of their mates by performing higher levels of offspring defense. Body color, mating system, and parental care in H. minckleyi appear to have evolved after it colonized Cuatro Ciénegas, and are likely a result of evolution in an isolated, stable environment.
Largemouth Bass Micropterus salmoides ranges naturally in Mexico fromthe binational Rio Grande basin, including Cuatro Ciénegas valley in the state of Coahuila, southward and eastward through two adjacent Gulf Coast drainages, the Río San Fernando and Río Soto la Marina in Nuevo León and Tamaulipas. Within this range, Florida Bass ⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚ has been introduced into reservoirs in at least the Río Grande and Soto La Marina basins. To assess the conservation status of native Mexican bass, we study genetic variability within and among Largemouth Bass populations and the degree of genetic introgression by Florida Bass within them. We sampled numerous localities in Cuatro Ciénegas, the San Fernando and Río Soto la Marina basins, and Vicente Guerrero Reservoir, where Florida Bass was introduced. We examined restriction-fragment polymorphisms within the 12S and 16S ribosomal RNA mitochondrial DNA genes and genotypes at two allozyme and ⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚⬚- ment testing using the nuclear data. Largemouth Bass specimens possessed generally lower nuclear diversity, but higher mitochondrial diversity, than those of Florida Bass. Populations from Cuatro Ciénegas differed from those in the San Fernando and Soto la Marina basins. Nuclear analyses revealed three genetically pure populations in Cuatro Ciénegas (Charcos Prietos, Las Playitas, and Canal del Tío Julio), but hybrids in Río Garabatal and Mojarral Este. Another presumably pure Largemouth Bass population was found in Río El Tigre of the Soto La Marina drainage. Our results could be explained by geographic barriers, sexbiased dispersion, hybrid disadvantage, or selection for coadapted gene complexes. More extensive surveys are needed to fully assess the conservation status of native Largemouth Bass populations in México. We anticipate that these will reveal additional native diversity. Meanwhile, the remnant native populations delineated herein are important to protect and we advocate that their ranges be managed as genetic conservation areas.
Sharpnose shiner, Notropis oxyrhynchus, was recently listedas federally endangered Known from the Brazos and Colorado Rivers, but Colorado population believed to be introduced and now extinct Our species distribution models indicate sufficient habitat for the species to occur in the Colorado (Fig. 3). Our previous work (Fig. 1) to verify cyprinid museum specimens in the Colorado indicate 5 records of N. oxyrhynchus collected from 1884 to 1955 strongly suggesting nativity of the species (or a morphologically similar form) Visual examination of specimens from the Colorado suggest distinctive morphological (shape) differences compared to Brazos specimens We hypothesized Colorado population might be a separate or incipient species