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Habilidades Competitivas de Plantas Raras y Comunes: Comparaciones Utilizando Acaena (Rosaceae) y Chionochloa ( Poaceae) de Nueva Zelanda
Author(s) -
Lloyd Kelvin M.,
Lee William G.,
Wilson J. Bastow
Publication year - 2002
Publication title -
conservation biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.2
H-Index - 222
eISSN - 1523-1739
pISSN - 0888-8892
DOI - 10.1046/j.1523-1739.2002.01033.x
Subject(s) - rare species , biology , common species , competition (biology) , ecology , range (aeronautics) , poaceae , habitat , materials science , composite material
It is commonly suggested that rare plant species are poor competitors. However, the study of rarity and competitive ability has, like much of the research on rare species, been hindered by insufficient sample size, scarce use of experimental methods, and lack of comparison with common species. We used a within‐taxon comparative approach to test for differences in competitive ability between rare and common species in two genera, Acaena ( Rosaceae: six rare and four common species) and Chionochloa ( Poaceae: four rare and five common species). We grew plants in replicated experiments at two levels of soil fertility and with two levels of competition, in monoculture or mixed with the introduced grass Agrostis capillaris . Competitive response was measured as relative yield, relative tiller increase, and change in live‐leaf fraction. Rarity was measured by geographic range size, defined as the number of 10‐km grid squares occupied by each species in New Zealand. The relationship between competitive ability and geographic range size was tested with correlations. Within Acaena , four of the rare species had high competitive ability, but there was no general relationship between competitive ability and rarity at either high or low levels of fertility. Differences in competitive ability appeared related to differences in ecological distribution rather than to rarity or commonness in a geographic sense. Within Chionochloa , common species tended to be stronger competitors than rare species, with the relationship being significant at the low level of fertility. Several of the common Chionochloa species have expanded their geographic ranges relatively recently, consistent with their greater competitive ability. Conversely, rare Chionochloa species occupy specialized habitats that may be interpreted as refuges from competition. Disparate results from Acaena and Chionochloa do not support the notion that rare species are generally poor competitors. Although rare species may have low competitive ability in some cases, it should not be assumed to be a cause of rarity for all rare species.