ISOZYME VARIATION IN CALLIANDRA-CALOTHYRSUS (LEGUMINOSAE) - ITS IMPLICATIONS FOR SPECIES DELIMITATION AND CONSERVATION

Patterns of genetic diversity within and among populations of Calliand ra calothyrsus, an important multipurpose tree species, were examined using isozyme analysis. C. calothyrsus is a widespread species distrib uted throughout Central America and southern Mexico, across a variety of environments. Morphologically and ecologically distinct populations can be identified within this range, but they are currently considere d to represent a single species. C. calothyrsus has been introduced to many parts of the tropics, where it is cultivated as a source of fuel wood, animal fodder, green manure, and shade by rural communities. Som e of these introductions are known to have originated from Guatemala, but very little is known about the genetic diversity of either the nat ive or naturalized populations. Isozyme electrophoresis of 23 loci acr oss 17 populations of C. calothyrsus indicated that the majority of ge netic diversity was partitioned between populations (F-ST = 0.802) and that within-population heterozygosity was low (mean H-0 = 0.057). Nat uralized populations had lower than expected heterozygosities and were most similar to material from Santa Maria de Jesus, a natural populat ion in southern Guatemala. Four distinct groups of populations were id entified on the basis of Nei's genetic distances and Population Aggreg ation Analysis (PAA), and correlate with the morphological and ecologi cal differences that can be observed within the species. The results a re discussed in relation to species delimitation and conservation.