USGS Science⌕ Search
Home/Archive/USGS

USGS · 70200447

Patterns of species richness hotspots and estimates of their protection are sensitive to spatial resolution

Alexa McKerrow·Nathan M. Tarr·Matthew J. Rubino·Steven G. Williams
View original source ↗Export metadata ↓

Abstract

Aim Species richness is a measure of biodiversity often used in spatial conservation assessments and mapped by summing species distribution maps. Commission errors inherent those maps influence richness patterns and conservation assessments. We sought to further the understanding of the sensitivity of hotspot delineation methods and conservation assessments to commission errors, and choice of threshold for hotspot delineation. Location United States. Methods We created range maps and 30‐m and 1‐km resolution habitat maps for terrestrial vertebrates in the United States and generated species richness maps with each dataset. With the richness maps and the GAP Protected Areas Dataset, we created species richness hotspot maps and calculated the proportion of hotspots within protected areas; calculating protection under a range of thresholds for defining hotspots. Our method allowed us to identify the influence of commission errors by comparing hotspot maps. Results Commission errors from coarse spatial grain data and lack of porosity in the range data inflated richness estimates and altered their spatial patterns. Coincidence of hotspots from different data types was low. The 30‐m hotspots were spatially dispersed, and some were very long distances from the hotspots mapped with coarser data. Estimates of protection were low for each of the taxa. The relationship between estimates of hotspot protection and threshold choice was nonlinear and inconsistent among data types (habitat and range) and grain size (30‐m and 1‐km). Main conclusions Coarse mapping methods and grain sizes can introduce commission errors into species distribution data that could result in misidentifications of the regions where hotspots occur and affect estimates of hotspot protection. Hotspot conservation assessments are also sensitive to choice of threshold for hotspot delineation. There is value in developing species distribution maps with high resolution and low rates of commission error for conservation assessments.

Explore related subjects

Diversity and DistributionsArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Alexa McKerrow, Nathan M. Tarr, Matthew J. Rubino, Steven G. Williams. 2018-05-23. Patterns of species richness hotspots and estimates of their protection are sensitive to spatial resolution. https://doi.org/10.1111/ddi.12779

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Null models reveal differing drivers of multidimensional beta diversity change in invaded metacommunities

Aim Invasion-driven changes in beta diversity (Δβ) are multifaceted (taxonomic, functional, and phylogenetic) and are comprised of three components (total beta diversity, replacement, and richness difference); therefore, they represent a nine-dimensional phenomenon. Invasion-driven trajectories of multidimensional Δβ are inconsistent and can vary based on the geographic origin of nonnative species, native community structure, and site attributes. Here, we examine the drivers of multidimensional Δβ to better understand how nonnative species alter biodiversity. Location 1023 wadable-stream fish communities across the conterminous United States. Methods We characterized nine dimensions of Δβ as changes in local contribution to beta diversity (ΔLCBD) derived from pairwise beta diversity of all 1023 sites between contemporary and native-only assemblages at each site. We used redundancy analysis and variance partitioning to identify and estimate the relative importance of 18 Δβ drivers related to nonnative species origin, propagule pressure, abiotic factors, and native community structure. We compared results between those from raw and null model standardized LCBD. Results We found an overall trend of taxonomic homogenization due to nonnative species occurrences. However, null model standardization revealed inconsistent directional change in functional and phylogenetic Δβ, and also revealed Δβ patterns and drivers that differed from those of raw values. Sites did not contribute evenly to overall Δβ trends, with nonnative species origin and native community structure explaining the most variation in ΔLCBD (16% and 15% respectively). Nonnative occurrences, regardless of origin, contributed to taxonomic homogenization, with the magnitude of change dependent on origin. Native community structure dictated the direction of phylogenetic Δβ, with phylogenetically distinct sites contributing to homogenization. Conclusions Our findings demonstrate the utility in using LCBD to identify site-level drivers of Δβ and the need for null model standardization of multidimensional Δβ metrics. Additionally, our results show that spatially explicit definitions of nonnative species are needed to gain robust estimates of Δβ.

conterminous United States↗
USGS2026

Predicted range shifts of non‐native grasses in response to climate change are influenced by photosynthetic pathway: A case study in the Hawaiian Islands

Aim Grasses comprise three main photosynthetic pathway variants (C 3 -BOP, C 3 -PACMAD and C 4 -PACMAD hereafter referred to as C 4 ). We sought to confirm climate niche differences among these photosynthetic pathway variants and assessed whether predicted non-native grass range shift patterns with climate change differ among photosynthetic pathway variants. Location Hawaiian Islands. Methods We used a species distribution modelling (SDM) approach that uses global occurrence records to inform local SDM based on local (Hawaiian Islands) occurrences. We compared climate niches and projected climate-driven range shifts, assuming moderate climate change (RCP 4.5, end of century), among 22 non-native grasses representing C 3 -BOP, C 3 -PACMAD and C 4 photosynthetic pathway variants. Results C 4 grasses exhibited the warmest temperature niches on average, but did not differ substantially in rainfall niche versus C 3 -BOP grasses. C 3 -PACMAD species averaged high suitability across a broad range of temperatures and rainfall conditions, except extreme aridity. In response to projected climate change, C 4 grasses had projected range increases. C 3 -BOP grasses typically responded with net range decreases, while C 3 -PACMAD grasses had variable range responses. However, patterns were contingent on elevation: for instance, the projected expansion of C 4 grasses was generally limited to elevations below 2000 m, with the largest increases in areas up to ~750 m. Areas of greatest reduction for C 3 -BOP and C 3 -PACMAD were projected at 750–1900 m and 100–1100 m elevation, respectively. Above 2000 m, range increases were projected for both C 3 grass variants. Main Conclusions Our projections suggest that non-native C 4 grasses pose the greatest risk for increasing spread and impacts under RCP 4.5, while certain C 3 -PACMAD grasses may endanger valuable high-elevation habitats. Photosynthetic pathway may be a useful component of weed risk assessment to evaluate how species may respond to climate change as similar range response patterns may be expected for other non-native grasses in other tropical and subtropical regions.

Hawaii↗
USGS2026

Changes in spatial distribution and abundance together determine potential for population persistence for greater sage-grouse

Aim Population ecologists often focus on changes in the distribution and abundance of wildlife species, which are useful for trend analyses and status assessments. However, rarely are these responses evaluated simultaneously for a single species, despite their unique contributions to fully assess a species' viability. For example, focusing solely on total abundance can mask important losses in overall distribution within a metapopulation structure that may contribute to long-term population instability that results from the extirpation of small peripheral populations. Location Bi-State region of Nevada and California, USA. Methods We simultaneously evaluated changes in population abundance and distribution for greater sage-grouse (hereafter sage-grouse; Centrocercus urophasianus ) within the Bi-State Distinct Population Segment (DPS), a genetically distinct and isolated population straddling the border of Nevada and California. We combined population counts, demographic data, and information on space use from marked individuals to evaluate changes in population distribution and abundance over three time periods that corresponded to the three most recent population nadirs (1995–2019, 2002–2019 and 2008–2019). Results The Bi-State DPS exhibited evidence of ~1.2%–2.5% declines annually, over the short/medium-term (1995–2019; λ^ = 0.987, 95% CRI: 0.970–0.999), short-term (2002–2019; λ^ = 0.975, 95% CRI: 0.963–0.985) and recent-term (2008–2019; λ^ = 0.988, 95% CRI: 0.973–1.001). Since 1995, the spatial distribution of sage-grouse abundance in the Bi-State DPS shifted amongst subpopulations, with peripheral subpopulations suffering the largest declines. Main Conclusions Gains in abundance and distribution amongst expanding subpopulations did not offset losses in the remaining subpopulations, with a net loss in occupied distribution of 156 km 2 since 1995. Reductions in spatial distribution could have implications for metapopulation persistence as peripheral populations become more vulnerable to stochastic events, which would not have been apparent from the evaluation of overall metapopulation abundance on its own.

California, Nevada↗