Risk assessment for the Mexican freshwater crayfish: the roles of diversity, endemism and conservation status

Abstract

ABSTRACT1. The freshwater fauna has been judged to be one of the most threatened biotic components in the world. In many tropical-temperate freshwater habitats worldwide the largest invertebrates are crayfish, as is the case with the cambarid crayfish in Mexico. With 98% of endemic species, most of them with reduced distribution ranges, the Mexican crayfish have not been analysed to examine how diversity, endemism and threat are distributed.2. A data set was analysed containing 1419 locality records for the 56 species of crayfish occurring in Mexico arranged in a 251 cell grid. Spatial autocorrelation analyses using Moran's I and G* were conducted; species richness, endemism and threat indices were calculated and mapped. An integrated risk score was derived from the two indices.3. Spatial autocorrelation analyses revealed a pattern that significantly departs from a random arrangement. Moran's I showed a positive autocorrelation between cells that are less than 800 km apart; while G* analysis identified one hotspot of diversity. Four areas with high endemism and seven areas with intermediate endemism values were recognized. The western portion of the Trans-Mexican Volcanic Belt, and some areas in the north are of special concern owing to the presence of threatened microendemic species.4. The areas where more threatened species occur differ from those with high endemism values. This distinction makes evident that for species with low dispersal capabilities the areas with high endemism are the product of historical and geological events, while the areas with high numbers of threatened species are those where human activities have had a major impact. The integrated risk score, however, resulting from the combination of endemism and threat, peaks along the Trans-Mexican Volcanic Belt and where it joins the Sierra Madre Oriental.5. The integrated risk score proposed in this study, based on well known and frequently used indices in conservation biology, can be used with existing data to determine areas where crayfish species richness, endemism and threat peak to make conservation efforts more cost-effective.

Define–Investigate–Estimate–Map (DIEM) Framework for Modeling Habitat Threats

“…Factors that put biodiversity at risk Natural threats: erosion, floods, droughts, disease, pests; human-induced threats: population pressure, overexploitation of biological resources, uncontrolled introduction of exotic species, poaching, fire, war; political threats Rangeland resources/biodiversity [23] Things that put the health and condition of ecosystems at risk Unconventional natural-gas development Watershed [24] Things that pose a risk to species richness and endemism Human activities Mexican freshwater crayfish conservation [25] Things that change species diversity, distribution, and conservation status. Activities that pose a risk to species richness and endemism…”

“…Studies have characterized existing perceived threats by using weights, the range of the threat, and the manner of impact (Table S1 in the Supplementary Materials). In the literature, habitat threats are measured using several indices to model how threats affect habitats [4,6,19,25,32]. Threat level is frequently cited as one of the major indices for explaining diversity patterns [13].…”

“…Similar index equations found in the literature were modified to be uniform. These equations include risk-based multispecies conservation value [10], threat score [21], ecological indicator ranking [6], ecological risk index [4,85], threat index [17,27,84], threat value [14], coastal vulnerability index [19], conversion threat index [32], relative threat factor severity index [23], endemism index [25], and habitat quality index [28]. Each of these index equations can be understood as habitat threat index equations on the basis of the broad definition of habitat threat.…”

Distribución espacial y conservación de cangrejos de agua dulce (Decapoda: Pseudothelphusidae) en Caldas, Colombia

“…Dada la importancia de estos cangrejos de agua dulce y su condición de especies endémicas, se pueden utilizar para delimitación áreas prioritarias para la conservación, como especies sombrilla, ya que, al conservarlas, se puede al mismo tiempo conservar otras áreas de interés para la biodiversidad asociada, debido a diversas interacciones y requerimientos (Richardson & Whittaker, 2010;Armendáriz et al, 2016;Escobar, 2020). Por lo tanto, el objetivo de la presente investigación fue establecer los patrones de distribución potencial de decápodos en el centro-occidente de Colombia, particularmente para Caldas, y aportar nuevo conocimiento sobre áreas importantes para la conservación de especies claves y endémicas, vinculadas a ecosistemas dulceacuícolas del departamento.…”

Population dynamics of the crayfish Cambarellus chapalanus from the San Juan Cosalá Mountain Range, Jalisco, Mexico

“…The family Cambaridae is found strictly in freshwater habitats and has an ample distribution in North America (Álvarez et al, 2012;Armendáriz et al, 2016;Crandall & Buhay, 2008). In Mexico, there are 3 genera (Cambarellus, Orconectes, and Procambarus) and 58 species of Cambaridae (Álvarez et al, 2012;Pedraza-Lara & Doadrio, 2015;Pedraza-Lara et al, 2021).…”