Gradient‐based habitat affinities predict species vulnerability to drought

Abstract

Ecological fingerprints of climate change are becoming increasingly evident at broad geographical scales as measured by species range shifts and changes in phenology. However, finer-scale species-level responses to environmental fluctuations may also provide an important bellwether of impending future community responses. Here we examined changes in abundance of butterfly species along a hydrological gradient of six montane meadow habitat types in response to drought. Our data collection began prior to the drought, and we were able to track changes for 11 years, of which eight were considered mild to extreme drought conditions. We separated the species into those that had an affinity for hydric vs. xeric habitats. We suspected that drought would favor species with xeric habitat affinities, but that there could be variations in species-level responses along the hydrological gradient. We also suspected that mesic meadows would be most sensitive to drought conditions. Temporal trajectories were modeled for both species groups (hydric vs. xeric affinity) and individual species. Abundances of species with affinity for xeric habitats increased in virtually all meadow types. Conversely, abundances of species with affinity for hydric habitats decreased, particularly in mesic and xeric meadows. Mesic meadows showed the most striking temporal abundance trajectory: Increasing abundances of species with xeric habitat affinity were offset by decreasing or stable abundances of species with hydric habitat affinity. The one counterintuitive finding was that, in some hydric meadows, species with affinity for hydric habitats increased. In these cases, we suspect that decreasing moisture conditions in hydric meadows actually increased habitat suitability because sites near the limit of moisture extremes for some species became more acceptable. Thus, species responses were relatively predictable based upon habitat affinity and habitat location along the hydrological gradient, and mesic meadows showed the highest potential for changes in community composition. The implications of these results are that longer-term changes due to drought could simplify community composition, resulting in prevalence of species tolerant to drying conditions and a loss of species associated with wetter conditions. We contend that this application of gradient analysis could be valuable in assessing species vulnerability of other taxa and ecosystems. Abstract. Ecological fingerprints of climate change are becoming increasingly evident at broad geographical scales as measured by species range shifts and changes in phenology. However, finer-scale species-level responses to environmental fluctuations may also provide an important bellwether of impending future community responses. Here we examined changes in abundance of butterfly species along a hydrological gradient of six montane meadow habitat types in response to drought. Our data collection began prior to the drought, and we were able to track changes for 11 years, of which eight were considere...

Large reorganizations in butterfly communities during an extreme weather event

“…The shifts in community composition during the drought year were most extensive at wetter, cooler sites (with high actual‐to‐potential evapotranspiration ratio, APET). Whilst counter to our prediction, this result is consistent with previous research: Debinski et al (, ) found that the most prominent changes in butterfly communities during a drought were in wet rather than dry meadows, potentially driven by shifts in vegetation towards drought‐tolerant plants. Indeed, plant community change in response to climatic perturbations can be more extreme in wetter rather than drier sites (Kardol et al ), while the condition of plants and their suitability as butterfly host‐plants may also be affected (Gibbs et al ).…”

Occupancy modeling of Parnassius clodius butterfly populations in Grand Teton National Park, Wyoming

“…clodius was more broadly distributed across the Teton region than expected based on previous studies in the area (Debinski et al 2006(Debinski et al , 2013, occupying 78% of the meadows we predicted would be suitable in 2013. These results are encouraging in the context of long-term population viability.…”

“…From 1997to 2007, Debinski et al (2006, 2010 collected vegetation and butterfly distribution data across this hydrological gradient within 55 montane meadows in the GYE, including 25 meadows in the Teton region. Butterfly abundance counts from these surveys indicated that Parnassius butterflies were most often found in mesic and xeric meadows (Debinski et al 2013). Furthermore, Auckland et al (2004) Of the 61 sites, 41 sites were surveyed as part of the study in 2013, three sites were not classified as potential habitat when ground-truthed and were removed from the study, nine sites were excluded due to inaccessibility (> 4.5 km from an access road), and the flight season ended before we were able to survey the remaining eight sites.…”

“…The other Parnassius species in the Teton region, Rocky Mountain Parnassian (Parnassius smintheus), has similar wing coloration of P. clodius and is present in low numbers in xeric meadows throughout the region (Debinski et al 2013). Due to the high similarity in phenotype, each Parnassius butterfly observed was caught with an insect net during surveys to verify species identity and was released unharmed at the end of the survey period.…”

Spatial patterns of meadow sensitivities to interannual climate variability in the Sierra Nevada

“…This pattern could potentially represent a gradient of water availability from xeric to mesic to hydric. Intermediate values also may be an indicator of mesic meadow types, which have been shown in other regions to exhibit higher sensitivities to climate variability relative to more xeric or hydric meadows (Debinski, Jakubauskas, & Kindscher, ; Debinski, Caruthers, Cook, Crowley, & Wickham, ; Debinski, Wickham, Kindscher, Caruthers, & Germino, ).…”