The impact of landscape disturbance on spatial genetic structure in the Guanacaste tree, Enterolobium cyclocarpum (Fabaceae).

This research investigated how changes in the environment impact the spatial genetic structure (distribution of different genetic elements) in the Guanacaste tree, a key species in Central America’s dry forests. The researchers found that this structure, in most cases, was significantly influenced by environmental factors such as tree densities, disturbances, and seed dispersal methods.

Research Background and Aim

• The researchers studied the Guanacaste tree (Enterolobium cyclocarpum), a major tree species in Central American dry forests.
• They aimed to understand how landscape disturbances like changes in plant densities and disturbances in the environment impact the tree’s spatial genetic structure (SGS).
• Understanding SGS gives crucial insights into population structure, genetic diversity, and consequently, the adaptability and survival potential of a species.

Study Sites and Disturbances

• Four sites in Costa Rica’s Guanacaste Province were chosen for the study.
• The sites varied in their conditions, with differing tree densities and levels of environmental disturbance.
• In disturbed areas (like pastures), Guanacaste trees are primarily dispersed by cattle and horses which are restricted in movement by pasture boundaries.

Methodologies and Findings

• The researchers used allozyme analyses, a method of studying different forms of enzymes to assess genetic variation within a species.
• This analysis showed significant levels of SGS in three out of the four sites studied.
• SGS was mainly due to clusters of young adults located along seasonal streams, rocky areas, and in abandoned pastures.

Correlation between Disturbance and SGS

• The least disturbed site that also contained the lowest density of large adult trees showed the highest SGS in the initial distance class.
• The site with the highest number of large adults located in individual pastures also had significant SGS, but it was low.
• In contrast, the semi-urban site without clusters of young adults did not exhibit SGS. This could be due to the absence of young adults to propagate the species.

Conclusion

• The evidence suggests that landscape disturbance has a strong influence on SGS patterns.
• This is consistent with a landscape model where the location of potential recruitment sites, restriction in seed disperser movements, and the number and location of maternal individuals drive the level and pattern of SGS.