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Mikania micrantha Kunth, commonly known as bitter vine, American rope, or mile-a-minute, is a rapidly growing vine, native to tropical America. Mikania micrantha is present in 20 Pacific island countries and territories, including Australia, the Cook Islands, Fiji, French Polynesia, Micronesia, Papua New Guinea, Samoa, Solomon Islands, and Vanuatu. A CLIMEX model based on native distribution of M. micrantha suggests that most of the islands in the Pacific, southern Asia, and parts of southern and central Africa are climatically suitable for M. micrantha, leaving these areas vulnerable to new or further incursions. Its rapid spread is a threat to both natural and agricultural environments, where it kills or reduces growth of preferred species, severely impacting on biodiversity and production. Large numbers of wind-dispersed seeds and ability to propagate vegetatively from stem fragments facilitate rapid invasion. Management of M. micrantha is difficult. Several postemergence herbicides exhibit some efficacy, but manual control via hand pulling and slashing is more commonly practiced. However, slashing may result in increased growth from fragments, and plants may regenerate from roots after herbicide application. Cultural techniques such as fallowing or burning may also help limit spread. Competitors that produce ample vegetation such as sweet potato (Ipomoea batatas [L.] Lam.) may be effective for suppression in some situations. Various studies have shown that Mikania micrantha exhibits some genetic diversity across biotypes encountered in southern Asia. Although little is currently known about its population genetics across the South Pacific, more information will undoubtedly facilitate potential for future biological control. A rust pathogen, Puccinia spegazzinii, introduced from South America was established in Taiwan in 2008, in Papua New Guinea and Fiji in 2009, and in Vanuatu in 2012 for biological control. The dodder Cuscuta campestris Yuncker has also shown some efficacy against M. micrantha, but its status as a known pest limits its use as a biological control agent. Recent research into the mikania wilt virus as a biocontrol agent is in its infancy, and it is too early to recommend it to assist with the management of M. micrantha. Given the difficulty of controlling M. micrantha once established and the early stages of research into biological control, high priority must be given to preventing colonization of Pacific islands where M. micrantha is not yet present, through early detection and rapid response to new incursions.
Traditional Hawaiian fishing and marine exploitation have been studied using both ethnographic and archaeological approaches, but few studies have attempted to investigate intensity of marine foraging over time at a regional scale. In this paper we examine Hawaiian exploitation of the marine eco-system of the leeward coast of Kohala, located on the northern tip of Hawai‘i Island. Over 158,000 specimens of fish, mollusks, arthropods, and echinoderms were recovered during archaeological excavation of 57 precontact (i.e., pre—AD 1778) residential features. These residences span a period of roughly 500 yr and are located both along the coast and in the interior. For these sites, we analyzed taxonomic abundance (NISP), number of taxa (NTAXA), taxonomic evenness, prey indices, and body-size changes over time. Results indicate that intensity of marine foraging increased over time, mirroring trends in increased numbers of residences (and inferred increases in human population size). There were no apparent declines in abundance of particular marine taxa. There were some differences in movement of marine resources into the upland Leeward Kohala Field System (LKFS), with larger-sized fish, mollusks, and echinoderms transported in increasing numbers. Examination of changes in body size suggest significant harvest pressure on fish and mollusks during the first 400 yr of human occupation and population rebound following human abandonment of the region in the postcontact period.
Invasive ants can influence abundance and diversity of insect pollinators, and this effect may be expected to be especially strong on oceanic islands. We examined abundance of native Hylaeus bees and patterns of flower visitation to three native Hawaiian plant species (Leptecophylla tameiameiae, Santalum haleakalae, and Geranium cuneatum) in presence and absence of invasive Argentine ants (Linepithema humile) in the subalpine shrubland of Haleakalā volcano. Native bees, nonnative honeybees, and microlepidoptera were responsible for the majority of visits to flowers of the three plant species. Ants visited flowers of S.haleakalae and G. cuneatum relatively commonly in ant-invaded zones but were less common or absent on flowers of L. tameiameiae in the same zones. Zones with ants had fewer Hylaeus bees in yellow pan traps than the zone without ants, and overall flower visitation rates to one plant species, G. cuneatum, were six times lower in sites containing ants. In one of two observation years, flower visitation to L. tameiameiae was also reduced in sites containing ants. Results suggest that Argentine ants may cause a reduction of native Hylaeus bee abundances; however, other factors correlated with elevation cannot be ruled out as the cause of differences in Hylaeus abundances across our sites.
Feral cats (Felis catus) have been shown to be a main contributor to species decline throughout the world and are especially threatening to insular species that lack appropriate defense characteristics. To mitigate the impact of feral cats on threatened species, space-use data are commonly used to design control strategies. In this article we report on the performance of GPS datalogging collars and provide baseline information on daily space use and home ranges of feral cats that threaten an endangered species on Rota Island in the Commonwealth of the Northern Mariana Islands. Using 100% Minimum Convex Polygon (MCP), average adult male home range was 1.32 km2 (n = 2) and average adult female home range was 0.22 km2 (n = 3). Home ranges were deemed fully revealed if asymptotes were approached using incremental analysis. Currently, there is no objective method for assessing where an asymptote is approached. Here, we describe a methodology to do so with the application of a Michaelis-Menten model to incremental data. We conclude that GPS datalogging collars are a viable tool for feral cat location data collection on Rota Island and that the Michaelis-Menten model is useful for determining asymptotic convergence of incremental location data.
Invasive nitrogen-fixing plants often increase energy and nutrient inputs to both terrestrial and aquatic ecosystems via litterfall, and these effects may be more pronounced in areas lacking native N2-fixers. We examined organic matter and nutrient inputs to and around anchialine ponds on Hawai‘i Island's leeward coast from an invasive, N2-fixing tree, Prosopis pallida, and a non-N2-fixing tree, Thespesia populnea. On a monthly basis we quantified: (1) tree basal area and stem density surrounding the ponds, and (2) nutrient content and quantity of P. pallida and T. populnea litter inputs. Tree density and basal area significantly predicted litterfall mass inputs for both species, but there was no difference in mean total annual litterfall mass, foliar N concentration, or litterfall N between the pond types. Time did not significantly influence litterfall mass, C, or P but did affect litterfall N, likely due to the production of P. pallida pods. In contrast, P concentrations were three times greater in T. populnea litter than in P. pallida litter, resulting in significantly higher P deposition where T. populnea was the prevalent tree species. Because this deposition of labile P by the non-N2-fixing T. populnea has the potential to strongly influence water quality and soil chemistry, its replacement by P. pallida in tree communities of lowland Hawai‘i may alter the functioning of anchialine pond ecosystems.
Passive integrated transponder (PIT) tags are an important technology used to study ecology and behavior of animals including several stream fishes. In this study we investigated feasibility of using PIT technology to study ecology of juvenile Mugil cephalus (striped mullet) in Hawaiian streams. We quantified retention rates of PIT tags relative to an alternative tagging approach, visible implant elastomer (VIE) tags in the postorbital adipose tissue, for juvenile M.cephalus through a laboratory study. Next we conducted a field study of movement patterns of PIT-tagged juvenile mullet in a lowland Hawaiian stream (Waiāhole Stream) from early to mid-August 2014. For the laboratory portion of the study, 30 individuals (5–7 cm fork length) were randomly distributed among three treatments: PIT, VIE, and control (no tag) and held for 48 days. Tag retention was 100% for PIT-tagged and 0% for VIE-tagged fish. For the field study, 19 individuals (14.6–18.7 cm fork length) collected from Waiāhole Stream were implanted with PIT tags, and the movement of tagged individuals between the stream and its stream-mouth estuary/Kāne‘ohe Bay was inferred using a stationary PIT antenna array for 7 days. During that period, the antenna array registered 189 detections (97% during daylight hours, one missed detection) from five individuals, translating into 27 visits in total. Trip lengths to the estuary ranged from 45 min to 22 hr, with longer forays (≥10 hr) occurring primarily at night and shorter forays (<10 hr) occurring throughout daylight hours. Our results suggest that PIT tags are a feasible and effective marking technology for studying ecology of individual M. cephalus in streams, which paves the way for future research using this approach to study other aspects of their ecology.
The leaf-mining moth genus Philodoria Walsingham (Lepidoptera: Gracillariidae) is composed of 30 described species, all of which are endemic to the Hawaiian Islands. Philodoria is known to feed on 10 families of endemic Hawaiian host plants, with several species recorded only from threatened or endangered hosts. Beyond their dependence on these plants, little is known of their evolutionary history and conservation status. We constructed a molecular phylogeny of Philodoria to assess validity of its current subgeneric classification and to help guide future work on this threatened Hawaiian lineage. Mitochondrial and nuclear DNA sequences from three genes (CO1, CAD, EF-1α) combining for a total of 2,041 base pairs, were collected from 11 Philodoria species, incorporating taxa from both currently recognized subgenera. These data were analyzed using both parsimony and model-based phylogenetic approaches. Contrary to the most recent systematic treatment of Philodoria, our results indicate strongly that the two currently recognized Philodoria subgenera are not monophyletic and that morphological characters used to classify them are homoplasious. Based on our robust results, we revised the higher classification of Philodoria: the subgenus EophilodoriaZimmerman, 1978 is established as subjective junior synonym of PhilodoriaWalsingham, 1907. We also present new host plant and distribution data and discuss host range of Philodoria as it pertains to endangered Hawaiian plants.
Five species of Gonocephalus lizards (N = 27) from Peninsular Malaysia were examined for gastrointestinal helminths: Gonocephalus abbotti (n = 6), Gonocephalus bellii (n = 8), Gonocephalus chamaeleontinus (n = 4), Gonocephalus grandis (n = 5), Gonocephalus robinsoni (n = 4). The aggregate helminth community consisted of two species of Cestoda, represented by Oochoristica javaensis and cysticercoid and nine species of Nematoda: Abbreviata borneensis, Cosmocercoides malayensis, Falcaustra malaysiaia, Meteterakis singaporensis, Orneoascaris sandoshami, Strongyluris calotis, Physocephalus sp., Physalopteridae gen. sp., Ascarididae gen. sp. Species of Gonocephalus are infected by generalist helminths that have potential for infecting a variety of lizards. Twenty-one new host records are reported.