Demographic spatial genetic structure of the Neotropical tree, Jacaranda copaia

Area of Science:

• Ecology
• Population Genetics
• Forest Science

Background:

• Understanding spatial genetic structure is crucial for forest management and conservation.
• Neotropical trees like Jacaranda copaia face unique ecological challenges impacting population dynamics.
• Demographic shifts can significantly influence genetic patterns within tree populations.

Purpose of the Study:

• To investigate changes in spatial genetic structure across different demographic stages of Jacaranda copaia.
• To correlate genetic differentiation and relatedness with tree size and demographic history.
• To evaluate potential mechanisms driving observed genetic patterns in this Neotropical tree species.

Main Methods:

• Utilized microsatellite genotypes from six loci.
• Analyzed demographic data from a large mapped forest plot.
• Compared genetic differentiation (FST) and relatedness (FIJ) across seed rain, seedlings, juveniles, and adult diameter classes.

Main Results:

• Seedlings exhibited significant genetic differentiation from other diameter classes (FST: 0.006–0.009).
• Seedlings showed excess homozygotes, indicating biparental inbreeding in reproductive adults.
• Relatedness increased substantially with tree diameter (FIJ: 0.011 for 1–26 cm to 0.110 for >56 cm).

Conclusions:

• Observed genetic patterns are consistent with overlapping generations and infrequent, high-recruitment events.
• Non-equilibrium population dynamics, driven by stochastic regeneration in light gaps, shape genetic structure.
• Low genetic structure in smaller size classes reflects high mortality and infrequent successful regeneration cycles.