A numeric, geographic and structural analysis of the Hakea falcata group (Proteaceae)

Specimens placed earlier under Hakea falcata are shown to comprise four species: H. falcata, H. ulicina, H. erecta and H. cygna. Failure by previous authors to cite types, or the correct type, led to the placement of subsequently collected H. falcata specimens (sensu R. Br.) under H. ambigua in Australian herbaria. The relationships of the five taxa are explored phenetically using metric multidimensional scaling and cluster analysis. Flowers provide the best diagnostic characters for separating H. falcata and H. ambigua , while fruits and seeds are better for H. erecta and H. cygna. All species are endemic to SW Australia, except H. ulcina , which is endemic to SE Australia. Two subspecies of H. cygna are recognized, based on populations with disparate leaf morphology. Each taxon has a distinctive leaf anatomy with all but H. falcata highly sclerophyllous.     

Developmental plasticity in a meristic character: the number of tentacles in the lophophore of a bryozoan species

There is increasing interest among evolutionary biologists in developmental plasticity. Previously ignored by many as being irrelevant to evolution because a plastic response to an environmental change is not inherited, the current, more positive, view of plasticity focuses on the fact that, although any individual plastic response is nonheritable, the overall pattern of developmental response to environmental variation (i.e. the developmental reaction norm) is heritable and may vary among genotypes within a population. Characters subject to plastic variation, like those that are entirely genetically determined, may vary in continuous, meristic or discrete ways. Of these, the least work has been carried out on meristic variation. In the present study, we contribute to the rectification of this imbalance by examining the plastic response of the number of tentacles in the lophophore of a species of bryozoan, Membranipora membranacea, to three environmental variables: temperature, salinity and food concentration. Because the approach taken was an experimental one, unlike the majority of studies of bryozoan tentacles to date, we are able to make statements about the causality of variation in tentacle number. The main conclusions of the present study are: (1) that plastic responses occur to all three environmental variables; (2) that these are part of a more generalized plastic response in the overall development of the zooids rather than being lophophore‐specific; and (3) that the issue of whether the relevant developmental reaction norms are adaptive or not is an open (and interesting) question. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 541–551.