Levels of allozyme diversity in closely related toadflaxes (Linaria, Plantaginaceae) and their correspondence with the breeding systems of the species

Abstract

Toadflaxes (Linaria Miller) represent the largest genus of the tribe Antirrhineae (formerly included in the Scrophulariaceae) of the Plantaginaceae family. These taxa vary according to their ranges (narrow-regional–widespread), biological traits (duration, flower morphology, breeding system) and ecological preferences. No comparative genetic studies have been performed up to the moment and the levels and distribution of genetic diversity within this genus remain undocumented. We have conducted an allozyme study in 8 taxa of Section Supinae. Five of them are narrow endemic, self-incompatible, insect-pollinated outcrossers that inhabit relatively unaltered habitats. The other three taxa are widespread, small-flowered selfers that inhabit crops subjected to high levels of recurrent disturbance. Linaria taxa showed moderate to high levels of genetic diversity. Parameters of genetic diversity were directly addressed to differences in breeding systems. Mean number of alleles per locus, total genetic diversity and genetic diversity within populations were higher among the outcrossers than among the selfers, (A e = 2.28 vs. 1.23; H T = 0.24 vs. 0.13; H S = 93.99% vs. 54.2%) while genetic diversity among populations and population differentiation were lower for the outcrossers than for the selfers (D ST = 0.02% vs. 45.98%; G ST = 0.03 vs. 0.52). Gene flow within and among populations produced a higher number of different genotypes (mean N G = 16 for outcrossers vs. 5.4 for selfers) and migrants (mean N m = 4.58 for outcrossers vs. 0.84 for selfers) that were attributed to an effective pollinator service in outcrossing populations. Differences in the levels and distribution of the genetic diversity are discussed in relation to biological and autoecological constraints of each group of taxa.