Population isolation in the Plains spadefoot toad: causes and conservation implications

Area of Science:

• Ecology and evolutionary biology
• Conservation genetics
• Amphibian research

Background:

• Geographic range disjunctions are common but can result from sampling bias, colonization, or habitat shifts.
• Habitat fragmentation due to human activity necessitates understanding disjunctions for conservation.
• The Plains spadefoot toad (Spea bombifrons) has a wide distribution but a suspected disjunct population in southern Texas.

Purpose of the Study:

• To investigate the putative disjunct population of Spea bombifrons in southern Texas.
• To determine if the southern Texas population is geographically isolated and genetically distinct.
• To assess the conservation status and future risks for this population.

Main Methods:

• Geographic Information System (GIS) mapping to delineate ranges.
• Species distribution modeling to predict habitat suitability.
• Population genetic analysis to assess genetic distinctness.

Main Results:

• Confirmed the southern Texas population of Spea bombifrons is geographically disjunct.
• Established that this population is genetically distinct from other Spea bombifrons populations.
• Species distribution modeling with climate projections indicates a high risk of local extinction for this population.

Conclusions:

• The southern Texas population of Spea bombifrons represents a unique, isolated lineage.
• Urgent conservation strategies are needed to protect this distinct amphibian population from extinction.
• Understanding range disjunctions is critical for effective biodiversity conservation in fragmented landscapes.