Unexpected evolutionary diversity in a recently extinct Caribbean mammal radiation

Area of Science:

• Evolutionary biology
• Island biogeography
• Paleogenomics

Background:

• Island ecosystems are crucial for studying evolution but are vulnerable to extinctions.
• The Caribbean has experienced high mammalian extinction rates, complicating evolutionary pattern identification.
• Oryzomyine rice rats represent a key extinct mammal group in the Caribbean.

Purpose of the Study:

• To reconstruct the evolutionary history of Caribbean oryzomyine rice rats using ancient DNA.
• To identify colonization events and diversification patterns in the Lesser Antilles.
• To understand the role of Late Miocene geomorphology in facilitating species dispersal.

Main Methods:

• Ancient DNA analysis of prehistoric Caribbean mammal material.
• Phylogenetic reconstruction to determine evolutionary relationships.
• Radiometric dating to establish colonization timelines.

Main Results:

• Identified two separate Late Miocene colonization events of the Lesser Antilles by distinct oryzomyine lineages from South America.
• Documented high phylogenetic diversification among Lesser Antillean oryzomyines, even in allopatric populations.
• Correlated oryzomyine colonization timing with other vertebrate taxa, suggesting a period of facilitated dispersal.

Conclusions:

• Late Miocene geomorphological conditions likely promoted simultaneous overwater dispersal of multiple South American lineages to the Caribbean.
• This study provides a crucial evolutionary baseline for the Caribbean, despite past extinctions.
• The Caribbean serves as a valuable natural laboratory for investigating island evolution dynamics.