Population Genetic Structure of Vallisneria americana, a Dioecious Clonal Macrophyte

Lokker, Cynthia; Susko, David J.; Lovett‐Doust, Lesley; Lovett‐Doust, Jon

doi:10.2307/2445294

Cited by 33 publications

(18 citation statements)

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“…It is not clear whether this contrasting behaviour results from differences in climate, in biotic interactions or in the physico-chemical properties of the lakes. From recent investigations it is known that aquatic macrophytes may genetically vary within a habitat, for example Vallisneria americana along a depth profile in Detroit River (Lokker et al, 1994). Different genotypes within a lake have also been shown for Phramites australis (Neuhaus et al, 1993).…”

Section: Discussionmentioning

confidence: 99%

Aquatic macrophytes as tools for lake management

Melzer

1999

The Ecological Bases for Lake and Reservoir Management

102

113

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Aquatic macrophytes can serve as useful indicators of water pollution along the littoral of lakes. In Bavaria, the submerged vegetation of about 100 lakes has been investigated by SCUBA diving over the past decade to evaluate the state of nutrient pollution. All lakes are marl lakes located in the northern calcareous alps and the prealpine region. The lakes differ in size, morphology, water residence time, nutrient loading, trophic status, recreational activities, and other characteristics. In all cases the entire shoreline of the lakes has been investigated. Among the investigated lakes are the three biggest Bavarian lakes, i.e. Lake Chiemsee, Lake Starnberg and Lake Ammersee. Mapping of the submerged vegetation occurred in four different depth zones, and variable shoreline sections. The length of each section was determined by the uniformity of the vegetation; as it changed, a new section was designated. Within each section and zone species were recorded and abundance of all observed macrophytes was estimated semi-quantitatively on a five-point scale. Nine different groups of macrophytes were recognised, including, in total, 45 different species of macrophytes. On the basis of this catalogue of indicator species, in combination with the abundance of the species, a 'macrophyte index' was devised, which ranges from 1 (unpolluted) to 5 (heavily polluted). Six groups of values of the macrophyte index, each represented by a different colour or grey-scale (in this publication), are presented to allow a clear illustration of the results. Important information for the successful restoration of lakes in Upper Bavaria has been obtained from the distribution patterns of the submerged vegetation. Many unknown waste water inflows or diffuse sources could be detected due to abrupt changes in the macrophyte index. Furthermore, the success of waste water removal by 'ring canalisation', resulting in a re-oligotrophication of many Bavarian lakes can be followed by changes in the macrophyte index.

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Section: Discussionmentioning

confidence: 99%

Aquatic macrophytes as tools for lake management

Melzer

1999

The Ecological Bases for Lake and Reservoir Management

102

113

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“…Ruckelshaus (1996) reported a slightly lower level (F ST = 0.154), also based on PGM loci, in a second population of this species. In contrast, little subdivision for isozyme loci was found in a population of V. americana in which F ST = 0.029 (Lokker et al, 1994), despite the fact that the female-male ratio increased with depth of water (Laushman, 1993).…”

Section: Introductionmentioning

confidence: 87%

Evidence for spatial structure and directional gene flow in a population of an aquatic plant, Potamogeton coloratus

1998

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Six hundred and forty-seven samples of Potamogeton coloratus from 60 ditches in the Gordano Valley, Somerset were analysed for variation at two polymorphic PGM isozyme loci using starch gel electrophoresis. A total of eight genotypes was detected, and a high level of partitioning of genetic variability between ditches was observed with F ST = 0.575. Genetic variability was shown to increase with distance from the head of the valley. The genetic subdivision of the population and pattern of increasing diversity downstream and downwind were attributed to genetic bottlenecks, associated with ditch cleaning events, and subsequent directional gene flow mediated by the prevailing wind and water currents.

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“…Spatial segregation of the sexes is a surprising phenomenon because in an immobile organism, separation of the sexes is expected to reduce the sexual reproductive success of individuals. Little is known about mechanisms responsible for this apparently nonadaptive pattern, although spatial segregation of the sexes is widespread, occurring in Ͼ30 plant species from 20 families (reviewed by Bierzychudek and Eckhart 1988, Iglesias and Bell 1989, Korpelainen 1991, Shea et al 1993, Lokker et al 1994, and has been suggested to have a role in the evolution of dioecy (Freeman et al 1997). Before the discovery of sex-linked molecular markers, it was difficult to test hypotheses about the causes of adult sex-ratio bias in dioecious plants because, in most species, it was impossible to determine the sex of individuals prior to reproductive maturity Geber 1999, Geber 1999).…”

Section: Introductionmentioning

confidence: 99%

Gender-Specific Selection during Early Life History Stages in the Dioecious Grass Distichlis spicata

Eppley¹

2001

Ecology

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Bias in the adult sex ratio of a population, if not due to a biased primary sex ratio, may be due to differential mortality of males and females, which can occur during any life history stage. Yet, although adult sex-ratio bias is common in dioecious plant species, little is known about the demography of prereproductive individuals. Using a RAPD-PCR (randomly amplified polymorphic DNA) marker that co-segregates with female phenotype, I studied juvenile demography in the saltmarsh grass Distichlis spicata, which exhibits within-population sex-ratio variation (spatial segregation of the sexes) and has genetic sex determination. First, I surveyed populations of D. spicata to ascertain whether any environmental factor co-varies with local sex ratio, and I found that habitats with female majorities are located at significantly lower elevations in the marsh than are habitats with male majorities. In randomly collected seeds, the sex ratio was significantly biased toward females, but male and female seeds did not differ in mass. Using a subsample of these seeds, I conducted greenhouse and field experiments to examine whether differences in seed germination or seedling survival between the sexes explain sex-ratio variation along the micro-elevation gradient in the marsh. In greenhouse treatments designed to mimic field habitats with female majorities, more male seeds germinated than did female seeds. In habitats with female majorities in the field, significantly more female seedlings survived an extreme high tide than did male seedlings (25.17% of females vs. 13.49% of males). These results suggest that, in habitats with female majorities, gender-specific bias in seedling survivorship, rather than seed germination, is a causal factor in the underlying sex-ratio bias. In habitats with male majorities, seed germination and seedling survival did not differ between the sexes. This study is the first to document environment-dependent differential seed germination and seedling mortality between males and females in a dioecious plant species.

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Population Genetic Structure of Vallisneria americana, a Dioecious Clonal Macrophyte

Cited by 33 publications

References 0 publications

Aquatic macrophytes as tools for lake management

Aquatic macrophytes as tools for lake management

Evidence for spatial structure and directional gene flow in a population of an aquatic plant, Potamogeton coloratus

Gender-Specific Selection during Early Life History Stages in the Dioecious Grass Distichlis spicata

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