Clonal reproduction and patterns of genotypic diversity in Decodon verticillatus (Lythraceae)

Abstract

Most perennial plants combine sexual reproduction with some form of clonal propagation. These mixed strategies may produce considerable variation among populations in levels of clonal diversity in response to ecological factors limiting one or other reproductive mode. Surveys of style morph frequencies in 163 populations of the eastern North American, clonal, tristylous aquatic, Decodon verticillatus (L.) Ell. (Lythraceae) suggested a wide range of clonal diversity among populations. Populations consisting of a single style morph were most common at the northern margin of the species' range and could have arisen through severe founder events followed by exclusive clonal propagation. Here, we test this hypothesis by comparing allozyme variation in populations monomorphic and polymorphic for style length located in Ontario and Michigan. Each of the four populations monomorphic for style length were fixed for a single three‐locus allozyme genotype while the seven trimorphic and five dimorphic populations contained an average of 26 multilocus genotypes each. Measures of genotypic diversity were high in polymorphic populations (average D = 0.93 ± 0.02 standard error; D = 0.00 for all populations monomorphic for style length). Three of the populations monomorphic for style length were fixed for a heterozygous genotype at one of the loci surveyed, suggesting that each consists of a single clone. In contrast, genotype frequencies in polymorphic populations conformed to Hardy‐Weinberg proportions indicative of sexual reproduction. The range of clonal diversity found in D. verticillatus is the largest reported for a clonal plant species, although the literature is too limited to determine whether this is truly unusual. Clonal diversity in D. verticillatus is likely to be regulated largely by ecological factors affecting seed production and establishment. However, genetically based sexual sterility also occurs in some populations.

Population Genetics of an Ecosystem-Defining Reef Coral Pocillopora damicornis in the Tropical Eastern Pacific

“…Comparisons among studies using the same marker and similar sampling indicate higher levels of clonality in peripheral populations (TEP, East Africa & Lord Howe Island) compared to more central populations (Indonesia & Great Barrier Reef)(Table 5). Higher clonality in peripheral populations has been observed in other corals [10], [115] and terrestrial plants [7], [116]. Clonal reproduction is considered to enable persistence in the commonly adverse environmental conditions towards range margins, at the expense of sexual reproduction benefits [117].…”

Severely reduced sexual reproduction in northern populations of a clonal plant, Decodonverticillatus (Lythraceae)

“…In June 1997, 9–13 cuttings (mean = 12) were collected from throughout each of the 18 monomorphic populations and seven of the 10 trimorphic populations, rooted and grown under standard glasshouse conditions (Dorken 1998). Each plant was then assayed following Eckert & Barrett (1993b) for its genotype at three polymorphic allozyme loci, all of which can be reliably scored and obey strict Mendelian segregation (Eckert & Barrett 1994b). We calculated the number of distinct three‐locus genotypes detected per sample ( G ) as well as a measure of genotypic richness, R = ( G − 1)/( n − 1), which varies from 0 when all n plants in a sample possess the same genotype, to 1.0, when all plants possess a different genotype.…”

Genotypic Variation in Agamospermous Erigeron compositus (Asteraceae)

“…Measures of genotypic diversity-Several statistics derived to measure species diversity have been adapted for analyzing genetic diversity in clonal populations (Ell strand and Roose, 1987;Eckert and Barrett, 1993). For this study, three of these measures were calculated.…”