Pacific Science Volume 44, Number 3, 1990

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.


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    44:3 Table of Contents - Pacific Science
    (University of Hawaii Press, 1990-07)
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    Zooplankton of the Gulf of California after the 1982-1983 El Nino Event: Biomass Distribution and Abundance
    (University of Hawaii Press, 1990-07) Lavaniegos-Espejo, Bertha E. ; Lara-Lara, J Ruben
    From 23 March to 7 April 1984, we studied the responses of zooplankton populations to the 1982-1983 El Nino event in the Gulf of California. Twenty six stations were sampled for zooplankton distribution and abundance. Mean displacement volume was 388 cm3/lOOO m3 , a value higher than biomass values reported for the California Current and the eastern tropical Pacific. Maximum values (up to 60 mg/m3 of dry weight) were registered on the eastern shore of the gulf. At other stations biomass values ranged from 11.2 to 39.2 mg/m3 . No significant differences were observed in the mean biomass of the central gulf between spring 1983 and spring 1984. However, biomass increased in the southern gulf during spring 1984. Mean total abundance of zooplankton was 13% higher than in 1983. Coastal stations registered up to 31% of the total abundance. Copepods and cladocerans represented over 65% of mean total abundance and community structure differed from that in 1983: there were more copepods, euphausiids, tunicates, and siphonophores in 1984, and fewer cladocerans, ostracods, and red crabs (Pleuroncodes planipes). Similarity analysis showed two main assemblages: one in the central gulf (temperate zone), the other near the mouth (tropical zone). These two regions correspond to zones with different physical and primary production characteristics. The different responses seen in the central and southern gulf may reflect phytoplankton biomass and primary productivity dynamics. The El Nino event reduced the biomass in the southern part of the gulf, although the entire gulf in 1983 and 1984 showed higher biomass values than other eastern Pacific systems. Year-to-year differences may be less important than seasonal changes. The EI Nino phenomenon mainly affected the relative abundances of different taxa.
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    Changes in the Structure and Composition of a New Zealand Lowland Forest Inhabited by Brushtail Possums
    (University of Hawaii Press, 1990-07) Campbell, D.J.
    All specimens of 19 tree and 11 shrub species greater than 10 cm dbh (more than 3000 stems of trees and tree ferns) were labeled, measured, and mapped in 2.25 ha of lowland forest near Wellington, New Zealand. Their fate, growth, and additional recruitment were monitored in three surveys over 16 yr, from 1969 to 1985. During the vegetation study, movements, diet, density, and breeding success of the introduced Australian brushtail possum (Trichosurus vulpecula) were studied in the same area of forest. In the study plot the number of stems and their total basal area increased between 1969 and 1985. However, several species that are eaten by possums have suffered substantial losses of both stems and total basal area. These include Beilschmiedia tawa, Weinmannia racemosa, Metrosideros robusta, and the tree fern Cyathea medullaris. Species not eaten by possums have increased in both numbers and basal area. These include Hedycarya arborea, Cyathea smithii, Cyathea dealbata, and Laurelia novaezelandiae. During the study there has been a decline in basal area of emergent trees, an increase in basal area of canopy trees (but little increase in their numbers), and an increase in numbers and basal area of minor species and dead trees. If present trends in structure and composition of this lowland forest continue, the future forest will have a greater proportion of tree ferns and more short-lived, small-diameter species. Canopy height and species diversity are also likely to decrease.
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    Identity of Aralia bastardiana Decaisne
    (University of Hawaii Press, 1990-07) Frodin, D.G.
    Aralia bastardiana Decne., since its written description in 1864 [as Panax bastardianus (Decne.) Decne.] thought to be from Tahiti but never recollected there, is considered almost certainly to have been collected in the Marquesas. It is identical to Cheirodendron marquesense F. Brown, the name by which the Marquesanpimata, the only species of the genus outside the Hawaiian Islands, is usually known. A new combination, Cheirodendron bastardianum, is therefore made. Spirally arranged leaves, seemingly exceptional in Cheirodendron but depicted on the main shoot in Decaisne's illustration of Aralia bastardiana, also occur in juvenile plants and on reversion shoots of Hawaiian species, at least in C. trigynum subsp. helleri and C. platyphyllum subsp. kauaiense. A list of localities and specimens seen of C. bastardianum is given.
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    Chromosome Counts from the Flora of the Juan Fernandez Islands, Chile. III.
    (University of Hawaii Press, 1990-07) Sun, Byung Yun ; Stuessay, Tod F. ; Crawford, Daniel J.
    Thirty-four chromosome counts are reported from populations in 20 species from Masafuera in the Juan Fernandez Islands, Chile. New species counts are in Abrotanella crassipes (2n = 18), Carpobrotus aequilaterus (n = 9), Coprosma pyrifolia (n = 22), Drimys confertifolia (n = ca. 43), Euphrasia Jormosissima (n = 44), Parietaria debilis (n = 8), and UrticaJernandeziana (n = ca. 11). A new chromosomal level for Hypochoeris glabra (n = 12) also is provided. The taxonomic implications of certain of these counts are discussed. These data help extend chromosomal information for endemic taxa of the archipelago as part of broad evolutionary studies on the origin of the vascular plants. This study again emphasizes the absence of aneuploid or euploid chromosomal alterations during speciation within the archipelago.
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