A second spontaneous hybrid in the genusLeucaena (Leguminosae, Mimosoideae)

Alexander

et al. 2011

American J of Botany

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Alongside other recent findings, a comprehensive picture of the complex evolutionary dynamics of polyploidy in Leucaena is emerging that includes paleotetraploidization, diploidization of the last common ancestor to Leucaena, allopatric divergence among diploids, and recent allopolyploid origins for tetraploid species likely associated with human translocation of seed. These results provide insights into the role of divergence and reticulation in a well-characterized angiosperm lineage and into traits of diploid parents and derived tetraploids (particularly self-compatibility and year-round flowering) favoring the formation and establishment of novel tetraploids combinations.

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The complex evolutionary dynamics of ancient and recent polyploidy in Leucaena (Leguminosae; Mimosoideae)

Alexander

et al. 2011

American J of Botany

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“…Diploid Leucaena represent the majority of species in a genus known to be complicated by human translocation, polyploidy, and hybridization (e.g., Harris et al, 1994; Hughes and Harris, 1998; Hughes et al, 2002, 2007). Through the application of newly available data, dense sampling strategies, and complementary phylogenetic and population genetic approaches, we have clarified the evolutionary diversification of diploids.…”

Section: Discussionmentioning

confidence: 99%

Phylogenetic and population genetic analyses of diploid Leucaena (Leguminosae; Mimosoideae) reveal cryptic species diversity and patterns of divergent allopatric speciation

Bailey

2011

American J of Botany

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Findings from this study highlight the importance and utility of multilocus data in the recovery of complex evolutionary histories. The results are consistent with allopatric divergence representing the predominant mode of speciation among diploid Leucaena. These findings contrast with the potential hybrid origin of several tetraploid species and highlight the importance of human translocation of seed to the origin of these tetraploids. The recognition of one previously unrecognized species (L. cruziana) and the elevation of another taxon (L. collinsii subsp. zacapana) to specific status (L. zacapana) is consistent with a growing number of newly diagnosed species from neotropical seasonally dry forests, suggesting these communities harbor greater species diversity than previously recognized.

“…Artificial crossing experiments have shown that crossability among species is high (27). In addition, two named hybrids, L. ϫ mixtec, a putative sterile triploid between tetraploid L. leucocephala and diploid L. esculenta, and L. ϫ spontanea, a putative fertile hybrid between tetraploid L. leucocephala and L. diversifolia, have been proposed (26,28,29). Furthermore, several other putative hybrids found growing in backyards in south-central (S-C) Mexico (Fig.…”

mentioning

confidence: 99%

Serendipitous backyard hybridization and the origin of crops

Proc. Natl. Acad. Sci. U.S.A.

Robertson

et al. 2007

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Backyard gardens, dump heaps, and kitchen middens are thought to have provided important venues for early crop domestication via generation of hybrids between otherwise isolated plant species. However, this process has rarely been demonstrated empirically. For the majority of polyploid crops, it remains uncertain to what extent hybridization and polyploidization preceded domestication or were precipitated by human activities. Using archaeological, ethnobotanical, geographical, and genetic data, we investigate the extent and significance of predomestication cultivation, backyard sympatry, and spontaneous hybridization for the Mimosoid legume tree Leucaena, which is used as a food crop throughout south-central Mexico. We show that predomestication cultivation was widespread, involved numerous independent transitions from the wild to cultivation, and resulted in extensive artificial sympatry of 2-6 species locally and 13 species in total. Using chloroplast and rapidly evolving nuclear-encoded DNA sequences, we demonstrate that hybridization in Leucaena has been extensive and complex, spawning a diverse set of novel hybrids as a result of juxtaposition of species in cultivation. The scale and complexity of hybridization in Leucaena is significantly greater than that documented for any other Mexican plant domesticates so far. However, there are striking parallels between Leucaena and the other major Mexican perennial domesticates Agave and Opuntia, which show very similar domestication via backyard hybridization pathways. Our results suggest that backyard hybridization has played a central role in Mesoamerican crop domestication and demonstrate that the simple step of bringing species together in cultivation can provide a potent trigger for domestication.domestication ͉ Leguminosae ͉ Leucaena ͉ Mesoamerica