Chronic anthropogenic disturbances and aridity negatively affect specialized reproductive traits and strategies of edible fruit plant assemblages in a Caatinga dry forest

Abstract

Chronic anthropogenic disturbances and climate change are the main threats to biodiversity, acting as potential drivers of assembly reorganization in human-modified tropical landscapes. We aimed to understand how the reproductive traits of edible fruit plant assemblages respond to chronic disturbances and aridity in the Caatinga, a dry forest in northeastern Brazil housing a human population that greatly depends on natural resources for subsistence and is threatened by increasing aridity. The study was carried out across 20 permanent plots of Caatinga, covering gradients of chronic disturbances (livestock grazing, wood extraction and non-timber product exploitation) and aridity (1051 mm to 664 mm). We registered 24 native plant species with fruits that are edible for humans, which were classified according to their flowering/fruiting pattern, floral size and reward, sexual and reproductive systems, pollination systems, and fruit types. They were also grouped into two categories of reproductive strategies (generalists and specialists). We documented that chronic disturbances and aridity pose more negative than positive effects on the reproductive traits of edible fruit plants in terms of trait richness (negative: 29% of the traits; positive: 3.2%) and abundance (negative: 19.3%; positive: 3.2%). In general, we observed that 79.2% of the studied species had at least one reproductive trait that was negatively reduced by increased chronic disturbance and/or aridity in terms of trait richness and abundance. Overall, 75% of the edible fruit species have specialized reproductive strategies that were negatively affected by chronic disturbances and/or aridity. Specifically, individual or combined effects of chronic anthropogenic disturbances or aridity negatively impacted the richness and abundance of specialized reproductive traits such as supra-annual flowering and fruiting patterns and obligatory cross-pollinated edible fruit species. Also, in terms of richness, the reproductive functional diversity of specialized reproductive strategies was negatively affected by increasing aridity. Our findings indicate that in the expected future scenarios of increased land-use and climate change, the Caatinga could face a collapse in the offer of edible fruits to local human communities by impacting the provision of this ecosystem service.