What is left after sex in fragmented habitats? Assessing the quantity and quality of progeny in the endemic tree Prosopis caldenia (Fabaceae)

Abstract

Prosopis caldenia (caldén) is a commercially valuable tree endemic to Central Argentina, a region that holds one of the highest estimates of deforestation rates worldwide. Caldén woodlands within Córdoba province currently remain as a highly fragmented mosaic with a single continuous area of forest left. Here, we assess reproduction, seed predation, and progeny performance of trees growing in continuous forest, small forest fragments and isolation. By assessing both mutualistic and antagonistic interactions we aim to determine net fragmentation effects on the quantity and quality of the surviving progeny. Contrary to expectations, the probability of setting fruits and seeds as well as the levels of seed predation were similar among trees growing across the three contrasting landscape conditions. However, trees growing in isolation produced significantly larger numbers of flowers than trees growing in continuous forest. Thus, the absolute quantity of progeny left for potential recruitment was higher in isolated trees, despite their lower pollination efficiency. However, progeny generated in continuous forest significantly outperformed the progeny from forest fragments and isolated trees, which also suffered higher levels of mortality. Finally, the cumulative performance across all measured life stages was also significantly greater in continuous forest. Therefore, it is within the last continuous forest tract that progeny produced may successfully grow and survive in natural conditions. Assurance of long-term persistence of remaining caldén populations should involve the incorporation of propagules from the continuous forest together with effective restoration efforts to enable gene flow via pollen and seeds among populations through forest corridors.