REPRODUCTIVE ECOLOGY OF DUBAUTIA MENZIESII (THE HALEAKALĀ KŪPAOA) AND ITS INTERACTION WITH POLLINATORS IN HALEAKALĀ
Date
2024
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Abstract
Islands harbor a significant part of global biodiversity owing to their high level of species endemism, and they are also highly vulnerable to global change threats. Understanding plant reproduction is
vital to conserve and restore island plants, ecosystems, and ensure stable population dynamics.
Dubautia menziesii (Asteraceae) – The Haleakalā kūpaoa - is a common shrub endemic to the alpine
and subalpine ecosystem of Haleakalā volcano on Maui. The purpose of this study is to: (i)
characterize the breeding system of D. menziesii, (ii) identify its main pollinators, (iii) determine how
plant isolation affects seed set and seed parasitism and (iv) estimate the abundance of D. menziesii
and its flower resources in the habitat. For the breeding system, hand pollination treatments were
performed in the field and seed set was analyzed. To identify pollinators, flower-visiting insects were
observed on flowers in the field. To asses the role of isolation, seed set and parasitism were
determined for individuals at varying distances from the nearest flowering neighbor. To estimate
species abundance, the line-intercept method was used, and sampling plots were established.
Dubautia menziesii is self-incompatible and requires outcrossing to set seeds (67% seed set for
outcrossed flowers vs. 3% for manually self-pollinated flowers and bagged, unmanipulated flowers).
The most frequent flower visitors were endemic Hylaeus bees (44%), and non-native honeybees
(34%), followed by seed bugs Nysius spp. (15.9%). Isolation had no significant effect on parasitism
rate at 2 sites (r=0.17, p=0.25; r=-0.06 p=0,71; respectively) nor for seed set (r=-0.28, p=0.055; r=-
0.27, p=0.1; respectively), probably due to visits by non-native honeybees, which forage over greater
distances than Hylaeus. The high density of D. menziesii at high elevations on Haleakalā suggest that
it plays an important role in maintaining insect populations in these communities.
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Botany, Ecology, Conservation biology
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33 pages
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