BIOACOUSTICS IN NEW ZEALAND AND JAPAN

Although it is highly recognisable, relatively little is known about the repertoire composition and singing behaviour of the Hermit Thrush (Catharus guttatus). To address this, we recorded spontaneously singing males in two eastern populations (Halifax, NS (n = 11) and Hancock County, ME (n = 7)) and analysed the recordings with respect to repertoire size, basic song type characteristics and song syntax. Males had song type repertoires of 7–12 song types, and no song type sharing between individuals was observed within or between populations. While frequency-related structural characteristics of the song types were the same between the populations, song type duration (especially that of the introductory note) differed significantly. The song types within each repertoire could be categorised into high and low song types based on introductory note frequency, and these song type categories also differed with respect to the amount and distribution of spectral energy. In both populations, males sang with immediate variety, never repeating the same song type consecutively, and preferentially used some song-type to song-type transitions more than others. In addition, we found correlational evidence of changes in singing behaviour (e.g., the relative use of low versus high song types) over the course of the breeding season. We discuss these findings in the context of other songbird research as well as their implications for future work examining how Hermit Thrush males utilise their songs in defending territories and attracting mates.     

CONVERGENT EVOLUTION AS A GENERATOR OF PHENOTYPIC DIVERSITY IN THREESPINE STICKLEBACK

Convergent evolution, in which populations produce similar phenotypes in response to similar selection pressure, is strong evidence for the role of natural selection in shaping biological diversity. In some cases, closely related populations can produce functionally similar but phenotypically divergence forms in response to selection. Functional convergence with morphological divergence has been observed in laboratory selection experiments and computer simulations, but while potentially common, is rarely recognized in nature. Here, we present data from the North Pacific threespine stickleback radiation showing that ecologically and functionally similar, but morphologically divergent phenotypes rapidly evolved when an ancestral population colonized freshwater benthic habitats in parallel. In addition, we show that in this system, functional convergence substantially increases morphospace occupation relative to ancestral phenotypes, which suggests that convergent evolution may, paradoxically, be an important and previously underappreciated source of morphological diversity.     

AGE, GROWTH, AND REPRODUCTION IN NEW ZEALAND FUR SEALS

Growth and reproductive biology of New Zealand fur seals ( Arctocephalus forsteri ) were studied by examining 127 seals (57 females, 64 males) killed incidentally in fishing gear in New Zealand waters in 1996. Tooth sections were used to age the animals, and male and female reproductive organs were examined macroscopically and histologically. The maximum age observed was 22 yr for females and 12 yr for males. Males were significantly larger than females, but growth was similar up to 5 yr. Males reached sexual maturity between 5 and 9 yr of age, whereas females did so between 4 and 6 yr. The mean pregnancy rate in females was 0.69 (95% CI = 0.54–0.81).     

ANALYSIS OF SPATIAL AND TEMPORAL DIVERSITY AND DISTRIBUTION OF PORPHYRA (RHODOPHYTA) IN SOUTHEASTERN NEW ZEALAND SUPPORTED BY THE USE OF MOLECULAR TOOLS1

Molecular studies have shown that New Zealand’s rocky shores are a habitat for >30 species of Porphyra, but little is known of their seasonal and zonal distribution. The spatial and temporal distribution of bladed Porphyra gametophytes at Brighton Beach, southeast New Zealand, were monitored for 32 months. Molecular markers were used for species identification, and a total of nine species was observed as being present during this time. Two species, P. cinnamomea and Porphyra sp. “ROS 54,” were the most common, and both were present for most months, while the remaining seven species were present sporadically, for only a few weeks at a time. P. cinnamomea W. A. Nelson and Porphyra sp. “ROS 54” were most common in the midintertidal, and both showed a similar seasonality with the highest presence during spring. They also showed a similar trend of seasonal dieback resulting in at least 1 month (May) in two consecutive years when they were both absent. This is one of the few studies investigating spatial and temporal distribution within a genus and over a 3‐year period. Our results show no distinct intertidal zonation patterns within the genus, and we conclude that morphologically similar species in a similar habitat rely on physiological mechanisms for survival.     

INTERBREEDING OF LARUS NOVAEHOLLANDIAE SCOPULINUS AND LARUS BULLERI IN THE WILD IN NEW ZEALAND

Five cases of interbreeding between the Red-billed Gull Larus novaehollandiae scopulinus and the Black-billed Gull L. bulleri in the wild in New Zealand are described. Captive hybrids from the wild population were shown to be fertile. Comparison between two years' observations in the same colony suggests that interbreeding occurs only when isolated individuals with a strong readiness to mate are prevented from mating with conspecifics. Other cases of interbreeding in Laws spp. support this conclusion.     

MECHANISMS OF APOMIXIS IN ELYMUS RECTISETUS FROM EASTERN AUSTRALIA AND NEW ZEALAND

Megasporogenesis was examined in cleared ovaries of 23 accessions of hexaploid Elymus from southeastern Queensland, northeastern New South Wales, the Australian Capital Territory, and the South Island of New Zealand. Apomixis was confined to the 17 accessions that morphologically corresponded to E. rectisetus (Nees in Lehm.) Löve et Connor. Female meiotic development followed the Polygonum type. Apomeiotic development was delayed relative to meiotic development because of a lengthy period of MMC vacuolation and nuclear stretching that occurred in place of meiosis I. Amitosis was evident in up to possibly five percent of the MMC's during nuclear stretching. A subsequent mitotic division facultatively functioned as meiosis II or the first embryo-sac mitosis to yield a 2n megaspore dyad, a hemidyad with an incomplete crosswall, or a directly binucleate embryo sac. Nuclear stretching generally resumed in the chalazal daughter nucleus from the apomeiotic division, but was not seen later in embryo sac development. When a dyad formed, its chalazal member would enlarge and develop into the embryo sac. The organized embryo sac was of the conventional eight-nucleate, seven-celled structure prior to antipodal proliferation, regardless of meiotic or apomeiotic origin. Microsporocyte meiosis was normal in both sexuals and apomicts. Deposition of a slightly birefringent substance, possibly callose, was deficient around megasporocytes, megaspores, and microsporocytes in the apomicts.