Limestone Barrens



Reproductive Biology Research

The reproductive biology of rare plants species has implications for conservation management plans because the breeding system of a species influences the genetic diversity within and among populations of that species. For example, a species that is primarily self-fertilizing may have less genetic variation within populations, but more variation among populations. Conservation management plans have to consider this fact and capture as much of this variation as possible.

Mating Systems and Hybridization of Long's Braya and Fernald's Braya

Research (including by-hand-pollination, and analysis of floral morphology) was conducted in 2000 to determine the mating systems of Long's Braya and Fernald's Braya. This work showed that both species are primarily autogamous (ie. self-fertilizing), but that Long's Braya has a higher potential for outcrossing (the opposite of "inbreeding") than does Fernald's Braya.

This means that recovery efforts for both Long's Braya and Fernald's Braya should focus on preserving the entire geographical range of the existing population of both species, so that no variation is lost.

Some plants were found to have intermediate floral characters (indicating hybridization between the two species). Indeed, hybrid by-hand-pollinations resulted in seeds being produced.

This means that conservation efforts should also focus on minimizing hybridization between Long's Braya and Fernald's Braya in order to prevent the potential loss of both of these rare species.

Braya Flowerparts

Mating Systems and Hybridization of Barrens Willow

Barrens willow can reproduce both sexually and asexually. Asexual reproduction (ie. reproduction without sex) seems to be the predominate form of successful reproduction for Barrens Willow. As a result of wind and frost erosion, the main root collar of the typically horizontal parent plant degrades as young branches produce adventitious roots (ie. roots growing from unusual places, such as along stems and branches), eventually resulting in a radially distributed collection of young plants that are genetically identical.

Male Barrens Willow develop catkins and begin to release pollen in June. Female Barrens Willow develop catkins by July, undergo fertilization, and then release seeds in late July and early August. The amount of sexual reproduction (including the number of catkins produced per plant), and the sex ratio, varies significantly among populations.

Germination trials indicate that the germination success of Barrens Willow seeds is high. However, seedlings are rarely if ever found in the wild. Moreover, seeds do not grow when planted within experimental seed addition plots. Seedling success is even lower when the population is growing on human-disturbed habitats.

Willows are known to hybridize easily and therefore the Barrens Willow may well hybridize with other willows found on the "Limestone Barrens". Research efforts to determine such hybridization potential, as well as resulting genetic variation, are ongoing.

The reproductive biology of a rare plant species has important implications for conservation management plans.

Experimental pollinations: Long's Braya with and without pollination bags.


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