Genome Size Variation in a Hybridizing Diploid Species Complex in Anacyclus (Asteraceae: Anthemideae)

Abstract

Premise of research. Interspecific hybridization was hypothesized to explain the remarkable floral phenotype variation found in overlapping areas of distribution for several Anacyclus species. We aimed to investigate genome size in natural populations of three diploid Anacyclus species with special emphasis in their contact areas to explore patterns of variation as additional evidence supporting current hybridization in these areas. Methodology. Flow cytometry was used to estimate the genome size of 564 individuals of the species complex of A. clavatus, A. homogamos, and A. valentinus from 30 sites. Additionally, genome size variation of 173 first-generation synthetic hybrids between these three species was also studied and compared with the estimates obtained in sympatric sites. Pivotal results. Differences in genome size between A. clavatus and A. valentinus were significant in nonoverlapping areas of species distribution, whereas in overlapping areas, the variation increased, preventing a clear differentiation between species. In sympatric sites of A. clavatus and A. valentinus, individuals with intermediate genome sizes between them were also observed and were significantly similar to those obtained from the first-generation experimental hybrids between these species. Genome sizes of A. clavatus and A. homogamos did not differ enough to allow discrimination between these species. Conclusions. The patterns of genome size variation observed in sympatric populations of A. clavatus and A. valentinus support the occurrence of current gene flow between these species and the existence of contact areas in overlapping distribution areas where phenotypic and genomic variation increases.

The nature of intraspecific and interspecific genome size variation in taxonomically complex eyebrights

“…Instead, the observed differences are probably due to changes in numerous different repeats or low-copy sequences segregating within the Euphrasia gene pool. At present, it is hard to tell whether these presence/absence variants comprise numerous individual repeat copies or whether there are (also) larger-scale presence/absence variants such as the loss or gain of chromosome fragments, as hypothesized to be present in hybridizing species of Anacyclus ( Agudo et al , 2019 ; Vitales et al , 2020 ). The high frequency of hybridization in Euphrasia may lead to increased levels of structural rearrangements due to ectopic recombination, which may be more common between heterozygous genomic repeats ( Morgan, 2001 ).…”

The Mendelian inheritance of gynomonoecy: insights from Anacyclus hybridizing species

“…These intermediate phenotypes were also observed in current sympatric populations of A. clavatus and A. valentinus along their overlapping areas of distribution in the western Mediterranean (Humphries, ; Álvarez, ). Homoploid hybridization between these two species was suggested to explain current patterns of 45S rDNA site‐number variation in wild populations (Rosato et al., ), as well as genome size variation patterns across similar geographic areas (Agudo et al., ).…”

Hybridization as a biodiversity driver: The case of Veronica × gundisalvi

“…tenuifolia; Table 2). Intermediate DNA contents between those of the parental species have been observed in sympatric sites of other homoploid hybridizing species (e.g., Baack et al, 2005;Agudo et al, 2019), supporting the possibility that current hybridization processes could be taking place on these locations. Individuals of V. orsiniana appear a few meters away from the V. × gundisalvi individuals in the population found in Zaragoza, and V. tenuifolia subsp.…”