Alien Insects Dominate the Plant-Pollinator Network of a Hawaiian Coastal Ecosystem

Shay, Kimberly; Drake, Donald R.; Taylor, Andrew D.; Sahli, Heather F.; Euaparadorn, Melody; Akamine, Michelle; Imamura, Jennifer Lynn; Powless, Doug; Aldrich, Patrick

doi:10.2984/70.4.2

Cited by 16 publications

(7 citation statements)

References 73 publications

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“…On islands, these negative effects of non‐native species can be particularly pronounced because so many endemic species are vulnerable to novel predators and competitors, and the Hawaiian Islands are an excellent example of this (Loope et al., ). Non‐native species may also, however, form mutualisms with native species (Rodriguez, ; Pratt et al., ; Shay et al., ). Mutualisms are ubiquitous in nature (Bronstein, ).…”

Section: Discussionmentioning

confidence: 99%

“…At least during daytime hours, non‐native insects in this system appear to be facilitating outcrossing for most of the focal plants, particularly the endangered species, whereas native insects exhibit low diversity and low flower‐visitation frequency. Restoration and conservation in this and similar systems (e.g., Shay et al., ) going forward represents a challenge (Seastedt et al., ). Without knowing what the historical native pollinators for these native plant species may have been, we are unable to attempt exact restoration of historical interactions.…”

Section: Discussionmentioning

confidence: 99%

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Non‐native insects dominate daytime pollination in a high‐elevation Hawaiian dryland ecosystem

Aslan

Shiels²,

Haines

et al. 2019

American J of Botany

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PREMISE OF THE STUDY:Over one-third of the native flowering plant species in the Hawaiian Islands are listed as federally threatened or endangered. Lack of sufficient pollination could contribute to reductions in populations, reproduction, and genetic diversity among these species but has been little studied. METHODS:We used systematic observations and manual flower treatments to quantify flower visitation and outcrossing dependency of eight native (including four endangered) plant species in a dryland ecosystem in Hawaii: Argemone glauca, Bidens menziesii, Dubautia linearis, Haplostachys haplostachya, Sida fallax, Silene lanceolata, Stenogyne angustifolia, and Tetramolopium arenarium.KEY RESULTS: During 576.36 h of flower observations, only insects visited the flowers. Out of all recorded flower visits, 85% were performed by non-native species, particularly the honeybee (Apis mellifera) and flies in the family Syrphidae. Some plant species received little visitation (e.g., S. angustifolia received one visit in 120 h of observation), whereas others were visited by a wide diversity of insects. The endangered plant species were visited by fewer visitor taxa than were the common native plant species. For six of the focal plant species, bagging of flowers to exclude pollinators resulted in significant reductions in seed set. CONCLUSIONS:The flower visitor community in this system, although heavily dominated by non-native insects, appears to be facilitating pollination for multiple plant species. Non-native insects may thus be sustaining biotic interactions otherwise threatened with disruption in this island ecosystem. This may be particularly important for the studied endangered plant species, which exhibit fewer partners than the more common plant species.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Non‐native insects dominate daytime pollination in a high‐elevation Hawaiian dryland ecosystem

Aslan

Shiels²,

Haines

et al. 2019

American J of Botany

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“…Invasive ants, bees and wasps (e.g. A. mellifera, C. smaragdula, C. dentipes, Lassioglossum sp., H. strenuus and P. nasidans) now dominate pollinator webs in coastal areas of the Hawaiian Islands (Hopper 2002;Shay et al 2016;Shell et al 2017;Shay and Drake 2018). Not only do these invasive pollinators compete with H. anthracinus for floral resources (Lach 2008;Ing and Mogren 2020), but they may also compete for nest sites.…”

Section: Discussionmentioning

confidence: 99%

Invasive ants reduce nesting success of an endangered Hawaiian yellow-faced bee, Hylaeus anthracinus

Plentovich¹,

Graham²,

Haines³

et al. 2021

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Hawaii has a single group of native bees belonging to the genus Hylaeus (Hymenoptera: Colletidae) and known collectively as Hawaiian yellow-faced bees. The majority of the 63 species have experienced significant declines in range and population. In 2016, seven species received federal protection under the Endangered Species Act of 1973. Competitors and predators, such as invasive bees, wasps and ants, are thought to be important drivers of range reductions and population declines, especially at lower elevations where more non-native species occur. We evaluated the effects of invasive ants on nesting Hylaeus anthracinus using artificial nest blocks that allowed us to track nest construction and development. The blocks were placed in pairs at 22 points encompassing three sites on the north and east sides of Oahu. One block in each pair was treated with a sticky barrier to prevent access by ants, while the other block remained untreated. From December 2015 to December 2016, we monitored 961 individual nests in the blocks. Seventy percent of nests in control blocks were invaded by ants. Nests in treated blocks were more likely to produce at least one adult than nests in untreated blocks (38% vs. 14%, respectively). In untreated blocks, ants were the most common cause of nest mortality followed by lack of development, displacement (primarily by the competitor Pachodynerus nasidens) and presumed pathogens. The invasive ant, Ochetellus glaber was the only observed nest predator, although the big-headed ant, Pheidole megacephala was also present. Hylaeus anthracinus inhabits coastal strand habitat which occurs in a narrow band just above the high tide line. Nests at one site were destroyed due to a high wave event, highlighting this species’ vulnerability to sea level rise. Additionally, no adult bees or nests were observed at the points where yellow crazy ants, Anoplolepis gracilipes were established. An increased understanding of the factors limiting Hawaii’s yellow-faced bees will provide information for future conservation efforts that may include landscape-scale ant control, habitat restoration and translocations.

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“…Since human arrival in the Hawaiian Islands (~800 years ago) (Wilmshurst et al 2011), forest ecosystems have undergone major changes owing to high rates of species extinction and introduction (Boyer 2008;Elphick et al 2010). Studies of pollination in Hawai'i have observed both native and non-native birds and insects playing a role in pollination of native plants, as well as observations of nectar larceny by native and non-native birds (Cox 1983, Junker et al 2010, Pratt et al 2010, Koch & Sahli 2013, Aslan et al 2014, Hanna et al 2014, Freed et al 2016, Shay et al 2016). However, rates of pollination versus nectar larceny between birds and insects visiting native Hawaiian flora, in addition to factors affecting visitation, remain uncertain.…”

Section: Cyanea Longiflora Clermontia Persicifoliamentioning

confidence: 99%

Pollination and nectar larceny by birds and bees in novel forests of the Hawaiian Islands

2021

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The extinction of native species and introduction of non-native species may lead to the disruption of biotic interactions. Pollination is a critical ecosystem process that often requires mutualisms between animals and plants. Non-native animals may interact with native flowering plants, with the potential to pollinate or steal nectar (larceny) from flowers without pollination. In the Hawaiian Islands, many native plants have lost their original pollinators. Birds and insects are known to visit native plant flowers, but it is unclear whether they pollinate or steal nectar, whether native and non-native species differ in their interactions with flowers, and what influences visitation to flowers. On Oʻahu, we deployed camera traps and conducted in-person observations on four at-risk species of Hawaiian lobelioids (Campanulaceae). We observed birds, mammals, and insects visiting flowers, with a native bird and native bee visiting most frequently. Regardless of native versus non-native status, bees made contact with reproductive structures during most visits (90.5% of visits), while birds stole nectar during most visits (99.3% of visits). Bee and bird visitation increased with the number of flowers on focal plants. Bird visitation also increased with canopy cover and the number of nearby conspecific flowers and decreased with the number of nearby heterospecific flowers. Our results indicate that bees may pollinate plants that were historically bird-pollinated, while native and non-native birds have neutral or negative impacts on these plants. Broadly, we contribute to an understanding of how native plant pollination can be altered in changing ecosystems.

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Alien Insects Dominate the Plant-Pollinator Network of a Hawaiian Coastal Ecosystem

Cited by 16 publications

References 73 publications

Non‐native insects dominate daytime pollination in a high‐elevation Hawaiian dryland ecosystem

Non‐native insects dominate daytime pollination in a high‐elevation Hawaiian dryland ecosystem

Invasive ants reduce nesting success of an endangered Hawaiian yellow-faced bee, Hylaeus anthracinus

Pollination and nectar larceny by birds and bees in novel forests of the Hawaiian Islands

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