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Marine Ecology Progress Series

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MEPS 399:117-130 (2010)  -  DOI:

Polymorphism and variation in modular animals: morphometric and density analyses of bryozoan avicularia

Michelle C. Carter1,2,3,*, Dennis P. Gordon2, Jonathan P.A. Gardner1

1Centre for Marine Environmental and Economic Research, School of Biological Sciences, Victoria University of Wellington,  PO Box 600, Wellington 6140, New Zealand
2National Institute of Water & Atmospheric Research (NIWA), Private Bag 14901, Kilbirnie, Wellington, New Zealand
3Present address: 280 Braddon Road, Loughborough, Leicestershire LE11 5YX, UK

ABSTRACT: Avicularia are polymorphic zooids characteristic of most species of cheilostome bryozoans. We examined the morphological diversity of avicularia to elucidate morphometric patterns in 38 cheilostome species from 11 superfamilies collected from a range of depths (habitats) around New Zealand. Multivariate statistical analyses of 4 types of avicularia (adventitious, interzooidal, vicarious and vibracula) showed that vicarious and vibracula were morphometrically invariable, and vibracula morphometrically distinct, even though these 4 types are dissimilar in their relationships to progenitor zooids and colony budding pattern. Adventitious types showed extensive overlap in morphospace with interzooidal and vicarious types. No depth-related effect on either morphometric variation or colony density of avicularia was discerned over the depth ranges studied (<8, 20–300, and 600–1000 m). Inter-colony variability in avicularian density existed in some species, whilst the main contributor to morphometric grouping was the type of avicularia involved. Greatest avicularian density occurred in colonies of those species possessing 2 types of avicularia (e.g. Caberea spp. adventitious and vibracula). Adventitious avicularia were the most common type, were morphometrically diverse and occurred at higher densities within colonies than interzooidal and vicarious types. Such polymorphism, frequency and density of adventitious types in natural populations may represent an evolutionary shift towards maximisation of functional efficiency at a smaller spatial scale of the colony. By analysing polymorph variation we show how a modular development promotes flexibility in module production, arrangement and morphology.

KEY WORDS: Avicularia · Polymorphism · Morphometrics · Modularity · Bryozoa · Functional diversity · New Zealand

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Cite this article as: Carter MC, Gordon DP, Gardner JPA (2010) Polymorphism and variation in modular animals: morphometric and density analyses of bryozoan avicularia. Mar Ecol Prog Ser 399:117-130.

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