A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica

Michael Lawes, Pascale Taplin, Sean Bellairs, Donald Franklin

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Because wind pollination is inefficient over longer distances, plants dependent on it may suffer Allee effects (lower individual reproductive fitness with lower density). However, at higher density, individual reproductive fitness may suffer because of intraspecific competition. We investigate density-dependent effects, via stand size, on cone and seed production and seed germinability in a conifer endemic to tropical Australia. Callitris intratropica R. T. Baker & H. G. Smith is an obligate-seeding tree that often occurs in monodominant stands embedded within savannas and on the fringes of monsoon forests. We found that isolated trees (50-300 m from stands) were taller, of broader profile, and produced approximately twice the number of cones (~407 cones per tree) as those in large stands (~173 cones per tree), suggesting that monodominance generates intraspecific competition. The number of seeds per cone (27 seeds) was not related to stand size. However, a contrasting effect in which seed germinability was higher in large stands (~20 vs. <10 % in small stands) was approximately compensatory and consistent with an Allee effect of wind pollination. The net effect of an approximately even trade-off between cone production and seed germinability was that there was neither an Allee or density-dependent effect of stand size on fitness, measured as the number of germinable seeds per tree. Nevertheless, because the likelihood of cross-fertilisation declines with distance, the ability of C. intratropica to persist as very isolated individuals may be limited. 
    Original languageEnglish
    Pages (from-to)169-174
    Number of pages6
    JournalPlant Ecology
    Volume214
    Issue number1
    DOIs
    Publication statusPublished - Jan 2013

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    Callitris
    seed cones
    size effect
    reproductive biology
    trade-off
    conifers
    coniferous tree
    seed
    Biological Sciences
    seeds
    wind pollination
    Allee effect
    fitness
    intraspecific competition
    pollination
    seed productivity
    seed production
    fertilization (reproduction)
    seeding
    savanna

    Cite this

    Lawes, Michael ; Taplin, Pascale ; Bellairs, Sean ; Franklin, Donald. / A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica. In: Plant Ecology. 2013 ; Vol. 214, No. 1. pp. 169-174.
    @article{fbbc8b63af604209926359b8c1f2f58d,
    title = "A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica",
    abstract = "Because wind pollination is inefficient over longer distances, plants dependent on it may suffer Allee effects (lower individual reproductive fitness with lower density). However, at higher density, individual reproductive fitness may suffer because of intraspecific competition. We investigate density-dependent effects, via stand size, on cone and seed production and seed germinability in a conifer endemic to tropical Australia. Callitris intratropica R. T. Baker & H. G. Smith is an obligate-seeding tree that often occurs in monodominant stands embedded within savannas and on the fringes of monsoon forests. We found that isolated trees (50-300 m from stands) were taller, of broader profile, and produced approximately twice the number of cones (~407 cones per tree) as those in large stands (~173 cones per tree), suggesting that monodominance generates intraspecific competition. The number of seeds per cone (27 seeds) was not related to stand size. However, a contrasting effect in which seed germinability was higher in large stands (~20 vs. <10 {\%} in small stands) was approximately compensatory and consistent with an Allee effect of wind pollination. The net effect of an approximately even trade-off between cone production and seed germinability was that there was neither an Allee or density-dependent effect of stand size on fitness, measured as the number of germinable seeds per tree. Nevertheless, because the likelihood of cross-fertilisation declines with distance, the ability of C. intratropica to persist as very isolated individuals may be limited. ",
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    author = "Michael Lawes and Pascale Taplin and Sean Bellairs and Donald Franklin",
    year = "2013",
    month = "1",
    doi = "10.1007/s11258-012-0155-9",
    language = "English",
    volume = "214",
    pages = "169--174",
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    A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica. / Lawes, Michael; Taplin, Pascale; Bellairs, Sean; Franklin, Donald.

    In: Plant Ecology, Vol. 214, No. 1, 01.2013, p. 169-174.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica

    AU - Lawes, Michael

    AU - Taplin, Pascale

    AU - Bellairs, Sean

    AU - Franklin, Donald

    PY - 2013/1

    Y1 - 2013/1

    N2 - Because wind pollination is inefficient over longer distances, plants dependent on it may suffer Allee effects (lower individual reproductive fitness with lower density). However, at higher density, individual reproductive fitness may suffer because of intraspecific competition. We investigate density-dependent effects, via stand size, on cone and seed production and seed germinability in a conifer endemic to tropical Australia. Callitris intratropica R. T. Baker & H. G. Smith is an obligate-seeding tree that often occurs in monodominant stands embedded within savannas and on the fringes of monsoon forests. We found that isolated trees (50-300 m from stands) were taller, of broader profile, and produced approximately twice the number of cones (~407 cones per tree) as those in large stands (~173 cones per tree), suggesting that monodominance generates intraspecific competition. The number of seeds per cone (27 seeds) was not related to stand size. However, a contrasting effect in which seed germinability was higher in large stands (~20 vs. <10 % in small stands) was approximately compensatory and consistent with an Allee effect of wind pollination. The net effect of an approximately even trade-off between cone production and seed germinability was that there was neither an Allee or density-dependent effect of stand size on fitness, measured as the number of germinable seeds per tree. Nevertheless, because the likelihood of cross-fertilisation declines with distance, the ability of C. intratropica to persist as very isolated individuals may be limited. 

    AB - Because wind pollination is inefficient over longer distances, plants dependent on it may suffer Allee effects (lower individual reproductive fitness with lower density). However, at higher density, individual reproductive fitness may suffer because of intraspecific competition. We investigate density-dependent effects, via stand size, on cone and seed production and seed germinability in a conifer endemic to tropical Australia. Callitris intratropica R. T. Baker & H. G. Smith is an obligate-seeding tree that often occurs in monodominant stands embedded within savannas and on the fringes of monsoon forests. We found that isolated trees (50-300 m from stands) were taller, of broader profile, and produced approximately twice the number of cones (~407 cones per tree) as those in large stands (~173 cones per tree), suggesting that monodominance generates intraspecific competition. The number of seeds per cone (27 seeds) was not related to stand size. However, a contrasting effect in which seed germinability was higher in large stands (~20 vs. <10 % in small stands) was approximately compensatory and consistent with an Allee effect of wind pollination. The net effect of an approximately even trade-off between cone production and seed germinability was that there was neither an Allee or density-dependent effect of stand size on fitness, measured as the number of germinable seeds per tree. Nevertheless, because the likelihood of cross-fertilisation declines with distance, the ability of C. intratropica to persist as very isolated individuals may be limited. 

    KW - Allee effect

    KW - anemophily

    KW - coniferous tree

    KW - density dependence

    KW - endemic species

    KW - fitness

    KW - germination

    KW - height

    KW - intraspecific competition

    KW - life history trait

    KW - population decline

    KW - reproductive biology

    KW - savanna

    KW - seed production

    KW - stand structure

    KW - trade-off

    KW - tropical region

    KW - Australia

    KW - Callitris

    KW - Callitris intratropica

    KW - Coniferophyta

    KW - Widdringtonia cedarbergensis

    U2 - 10.1007/s11258-012-0155-9

    DO - 10.1007/s11258-012-0155-9

    M3 - Article

    VL - 214

    SP - 169

    EP - 174

    JO - Plant Ecology

    JF - Plant Ecology

    SN - 0042-3106

    IS - 1

    ER -