The effects of introduced ungulates on native and alien plant species in an island ecosystem: Implications for change in a diverse mesic forest in the Hawaiian Islands

Weller, Stephen G.; Sakai, Ann K.; Clark, Michelle; Lorence, David H.; Flynn, Timothy W.; Kishida, Wendy; Tangalin, Natalia; Wood, Ken R.

doi:10.1016/j.foreco.2017.11.023

Cited by 22 publications

(7 citation statements)

References 47 publications

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“…In spite of the myriad negative impacts widely described for non-native species on islands (Reaser et al, 2007;Mayol et al, 2017;Rogers et al, 2017;Weller et al, 2018), their role as rescuers of ecological functions, lost in the past with fauna extinctions, acquires great relevance under the current scenario of increasing defaunation (Dirzo et al, 2014;Malhi et al, 2016). Our results here support the Janzen and Martin (1982) anachronism hypothesis and suggest that non-native species can disperse effectively anachronistic fruits, exerting a fundamental role in insular ecosystems.…”

Section: Discussionsupporting

confidence: 77%

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

2019

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Section: Discussionsupporting

confidence: 77%

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

2019

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“…Current trends were considered decreasing for AOO, EOO, number of subpopulations, number of mature individuals, and quality and extent of habitat based on estimated or observed data, including effects of invasive weeds and animals (Weller et al., 2018); climate change, including more extreme temperatures and fluctuations in precipitation; and increase in stochastic events, such as landslides and hurricanes (Fortini et al., 2013).…”

Section: Methodsmentioning

confidence: 99%

Extinction risk of the endemic vascular flora of Kauai, Hawaii, based on IUCN assessments

Rønsted

Walsh

Clark

et al. 2022

Conservation Biology

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The International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) is the world's most comprehensive information source on the global conservation status of species. Governmental agencies and conservation organizations increasingly rely on IUCN Red List assessments to develop conservation policies and priorities. Funding agencies use the assessments as evaluation criteria, and researchers use meta‐analysis of red‐list data to address fundamental and applied conservation science questions. However, the circa 143,000 IUCN assessments represent a fraction of the world's biodiversity and are biased in regional and organismal coverage. These biases may affect conservation priorities, funding, and uses of these data to understand global patterns. Isolated oceanic islands are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates. The archipelago of Hawaii has one of the highest levels of endemism of any floristic region; 90% of its 1367 native vascular plant taxa are classified as endemic. We used the IUCN's assessment of the complete single‐island endemic (SIE) vascular plant flora of Kauai, Hawaii, to assess the proportion and drivers of decline of threatened plants in an oceanic island setting. We compared the IUCN assessments with federal, state, and other local assessments of Kauai species or taxa of conservation concern. Finally, we conducted a preliminary assessment for all 1044 native vascular plants of Hawaii based on IUCN criterion B by estimating area of occupancy, extent of occurrence, and number of locations to determine whether the pattern found for the SIE vascular flora of Kauai is comparable to the native vascular flora of the Hawaiian Islands. We compared our results with patterns observed for assessments of other floras. According to IUCN, 256 SIE vascular plant taxa are threatened with extinction and 5% are already extinct. This is the highest extinction risk reported for any flora to date. The preliminary assessment of the native vascular flora of Hawaii showed that 72% (753 taxa) is threatened. The flora of Hawaii may be one of the world's most threatened; thus, increased and novel conservation measures in the state and on other remote oceanic islands are urgently needed.

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“…The Laupāhoehoe Forest Reserve (LFR) site is managed by the State of Hawai'i Department of Land and Natural Resources; it is largely unfenced except for a small number of exclosures ranging in size from 0.1-3.5 ha within the study area. Ungulates, including cattle (Bos taurus), goats (Capra hircus), sheep (Ovis aries), mouflon (O. gmelini musimon), and pigs (Sus scrofa), are found across the island of Hawai'i, and each is a known agent of forest disturbance [26]. Because Hawaiian ecosystems evolved without pressures from ungulates and other large mammals, these animals are believed to disrupt succession and alter disturbance regimes [27] and are also suspected of spreading ROD through wounding and other mechanisms.…”

Section: Study Site Locationsmentioning

confidence: 99%

Spatial Patterns of ‘Ōhi‘a Mortality Associated with Rapid ‘Ōhi‘a Death and Ungulate Presence

Perroy

Sullivan

Benitez

et al. 2021

Forests

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Effective forest management, particularly during forest disturbance events, requires timely and accurate monitoring information at appropriate spatial scales. In Hawai‘i, widespread ‘ōhi‘a (Metrosideros polymorpha Gaud.) mortality associated with introduced fungal pathogens affects forest stands across the archipelago, further impacting native ecosystems already under threat from invasive species. Here, we share results from an integrated monitoring program based on high resolution (<5 cm) aerial imagery, field sampling, and confirmatory laboratory testing to detect and monitor ‘ōhi‘a mortality at the individual tree level across four representative sites on Hawai‘i island. We developed a custom imaging system for helicopter operations to map thousands of hectares (ha) per flight, a more useful scale than the ten to hundreds of ha typically covered using small, unoccupied aerial systems. Based on collected imagery, we developed a rating system of canopy condition to identify ‘ōhi‘a trees suspected of infection by the fungal pathogens responsible for rapid ‘ōhi‘a death (ROD); we used this system to quickly generate and share suspect tree candidate locations with partner agencies to rapidly detect new mortality outbreaks and prioritize field sampling efforts. In three of the four sites, 98% of laboratory samples collected from suspect trees assigned a high confidence rating (n = 50) and 89% of those assigned a medium confidence rating (n = 117) returned positive detections for the fungal pathogens responsible for ROD. The fourth site, which has a history of unexplained ‘ōhi‘a mortality, exhibited much lower positive detection rates: only 6% of sampled trees assigned a high confidence rating (n = 16) and 0% of the sampled suspect trees assigned a medium confidence rating (n = 20) were found to be positive for the pathogen. The disparity in positive detection rates across study sites illustrates challenges to definitively determine the cause of ‘ōhi‘a mortality from aerial imagery alone. Spatial patterns of ROD-associated ‘ōhi‘a mortality were strongly affected by ungulate presence or absence as measured by the density of suspected ROD trees in fenced (i.e., ungulate-free) and unfenced (i.e., ungulate present) areas. Suspected ROD tree densities in neighboring areas containing ungulates were two to 69 times greater than those found in ungulate-free zones. In one study site, a fence line breach occurred during the study period, and feral ungulates entered an area that was previously ungulate-free. Following the breach, suspect ROD tree densities in this area rose from 0.02 to 2.78 suspect trees/ha, highlighting the need for ungulate control to protect ‘ōhi‘a stands from Ceratocystis-induced mortality and repeat monitoring to detect forest changes and resource threats.

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The effects of introduced ungulates on native and alien plant species in an island ecosystem: Implications for change in a diverse mesic forest in the Hawaiian Islands

Cited by 22 publications

References 47 publications

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

Extinction risk of the endemic vascular flora of Kauai, Hawaii, based on IUCN assessments

Spatial Patterns of ‘Ōhi‘a Mortality Associated with Rapid ‘Ōhi‘a Death and Ungulate Presence

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