Are buffalograss (Buchloë dactyloides) cytotypes spatially and ecologically differentiated?

Area of Science:

• Plant genetics and evolutionary biology
• Ecology and biogeography
• Bioinformatics and population genetics

Background:

• Autopolyploidy is prevalent in dominant grasses, yet cytotype distribution within species remains largely unknown.
• Understanding cytotype distribution is crucial for comprehending species adaptation and ecological success.
• Buffalograss (Buchloë dactyloides) is a dominant grass species in the Great Plains, making it an ideal model for this research.

Purpose of the Study:

• To map the geographic distribution of cytotypes within buffalograss (Buchloë dactyloides).
• To investigate potential ecological differentiation between distinct buffalograss cytotypes.
• To provide insights into the evolutionary dynamics and adaptive potential of buffalograss.

Main Methods:

• Collected and sampled 578 buffalograss individuals range-wide, including herbarium specimens.
• Estimated cytotype using simple sequence repeat (SSR) markers, validated against chromosome counts.
• Assessed ecological differentiation using macroclimatic variables and niche modeling.

Main Results:

• SSR analysis accurately estimated cytotype in 89% of samples.
• Tetraploid cytotypes were predominantly found in the northwest, while hexaploids occupied the southeast range.
• Significant, albeit subtle, macroclimatic differences were identified between tetraploid and hexaploid cytotypes.

Conclusions:

• This study represents the most extensive analysis of cytotype niche differentiation in buffalograss to date.
• Buffalograss cytotypes exhibit non-random geographic distributions and varying frequencies.
• Distinct ecological niches occupied by common tetraploid and hexaploid cytotypes suggest adaptive differentiation.