Fitness and its variation among populations of Acacia tortilis subsp. raddiana in Southern Sinai, Egypt

Abstract

Acacia tortilis subsp. raddiana (Fabaceae) plays an important role in the life of desert animals and is a major source of livestock feed and firewood for the native Bedouin people in Southern Sinai, Egypt. High mortality and low juvenile recruitment has been reported in recent years leading to decline in population size and number of this species. Small populations tend to be subject to an increased probability of stochastic extinction due to demographic, environmental and genetic factors. Therefore, this study aims to determine if A. tortilis subsp. raddiana populations suffer reduced fitness and its correlation or association with genetic diversity and mating parameters. Correlations and association between fitness, population size, genetic variation, and mating system parameters were tested using Spearman correlation and simple regression analyses. Stepwise regression analyses were used to identify useful predictors for fitness. The results revealed that A. tortilis subsp. raddiana populations’ fitness is generally low to very low (0.1 ± 0.11). There was no relationship detected between A. tortilis subsp. raddiana fitness or population size and observed or expected heterozygosity. While there was no evidence for reduced fitness in A. tortilis subsp. raddiana populations, the study indicated that fitness is negatively associated with population size. Population size was associated also with the number of alleles (A) and number of alleles per polymorphic locus (A_P). The study came to the conclusion that although the low to very low values, there is no evidence for reduced fitness in Acacia tortilis subsp. raddiana small populations. Some of the studied populations (L6, L2, L3, and M4) are exceptionally fit which makes them the first candidates as seed source in restoration and both in situ and ex situ conservation efforts.

Key words: Acacia tortilis, Sinai, germination, establishment, fitness.