Wallace M. Meyer

Dramatic response to climate change in the Southwest: Robert Whittaker's 1963 Arizona Mountain plant transect revisited

Models analyzing how Southwestern plant communities will respond to climate change predict that increases in temperature will lead to upward elevational shifts of montane species. We tested this hypothesis by reexamining Robert Whittakers 1963 plant transect in the Santa Catalina Mountains of southern Arizona, finding that this process is already well underway. Our survey, five decades after Whittakers, reveals large changes in the elevational ranges of common montane plants, while mean annual rainfall has decreased over the past 20 years, and mean annual temperatures increased 0.25°C/decade from 1949 to 2011 in the Tucson Basin. Although elevational changes in species are individualistic, significant overall upward movement of the lower elevation boundaries, and elevational range contractions, have occurred. This is the first documentation of significant upward shifts of lower elevation range boundaries in Southwestern montane plant species over decadal time, confirming that previous hypotheses are correct in their prediction that mountain communities in the Southwest will be strongly impacted by warming, and that the Southwest is already experiencing a rapid vegetation change.

The horticultural industry as a vector of alien snails and slugs: widespread invasions in Hawaii

The horticultural industry is an important vector of alien snails and slugs. Surveys of nurseries in the Hawaiian Islands recorded 31 terrestrial snail/slug species, all but two of them alien and five previously unrecorded. Individual facilities had 1–17 species. In total, 38 non-native terrestrial snail/slug species have become established, originating globally. Numbers on each island do not reflect numbers of survey locations but rather the total numbers established on each island. Species richness and community composition in nurseries differed significantly among islands and among different-sized nurseries. Certain species were more common on Oahu (main port of entry to Hawaii) so most of these alien species may have been first introduced to Oahu and then spread to other islands. Some of them cause damage in nurseries. Some may cause shipments of nursery products to be rejected when they are inadvertently exported with them. When they are transported to and become established in new areas they may cause agricultural, horticultural and environmental problems. Greater awareness of these species is necessary in the nursery industry and among quarantine officials.

Feeding Preferences of Two Predatory Snails Introduced to Hawaii and Their Conservation Implications

ABSTRACT Two introduced predatory land snails, Euglandina rosea and Oxychilus alliarius, have been implicated in the decline of native Hawaiian and Pacific island land snails. We examined the feeding ecology of E. rosea and O. alliarius, focusing first on prey size and species preferences, and second on quantifying consumption rates, which is necessary to address the possible levels of impact on natural populations. In prey-size preference experiments, E. rosea always consumed more snails in the smaller size class. In prey-species preference experiments, E. rosea preferred snails to slugs but showed no preference among snail species. Size preference experiments indicated that O. alliarius will only consume prey less than 3 mm in shell length. In prey species preference experiments O. alliarius consumed every snail species offered but did not consume either of the slug species. Consumption rates were positively related to the size of the predator, with the larger predator, E. rosea, having a much higher consumption rate than O. alliarius, and with larger E. rosea consuming more than smaller E. rosea. These results have unfortunate conservation ramifications, because since they indicate that both E. rosea and O. alliarius are generalist snail predators feeding preferentially on the smallest snails, although they rarely eat slugs. Since many extant Hawaiian and Pacific island snail species are small, they are at risk of predation by these two introduced predators, while invasive slugs — there are no native slugs in Hawaii — may not be impacted by them.

Black Rat (Rattus rattus) Predation on Nonindigenous Snails in Hawai'i: Complex Management Implications

Abstract: Understanding interactions among nonindigenous species that pose a threat to native species is crucial to effectively preserve native biodiversity. Captive feeding trials demonstrated that the black rat, Rattus rattus, will readily consume two of the most destructive nonindigenous snails, the giant African snail, Achatina fulica (100% predation), and the predatory snail Euglandina rosea (80% predation). Rats consumed snails from the entire size range offered (11.5 to 59.0 mm shell length), suggesting that there is no size refuge above which snails can escape rat predation. Damaged E. rosea shells from the captive feeding trials were compared with shells collected in the Wai‘anae Mountains, O‘ahu. This revealed evidence that R. rattus is responsible for at least 7%–20% of E. rosea mortality. However, this is likely a substantial underestimate because 67% of E. rosea shells in the captive feeding trials were damaged in such a way that they would not have been collected in the field. Therefore, we hypothesize that reduction or eradication of R. rattus populations may cause an ecological release of some nonindigenous snail species where these groups coexist. As such, effective restoration for native snails and plants may not be realized after R. rattus removal in forest ecosystems as a consequence of the complex interactions that currently exist among rats, nonindigenous snails, and the remaining food web.

Giant African snail, Achatina fulica, as a snail predator

Individuals of Achatina fulica (Bowdich, 1822) were observed preying on veronicellid slugs at two sites on the island of Oahu, Hawaii. As such, the presence of A. fulica may pose a greater threat to terrestrial mollusc conservation than previously imagined. It is our hope that this note provides some impetus for other researchers to explore the possible predation impacts of introduced populations of A. fulica and to consider the possibility that other introduced snails and slugs may be having as yet unforeseen or unnoticed impacts.

Ground-Dwelling Arthropod Communities of a Sky Island Mountain Range in Southeastern Arizona, USA: Obtaining a Baseline for Assessing the Effects of Climate Change

The few studies that have addressed past effects of climate change on species distributions have mostly focused on plants due to the rarity of historical faunal baselines. However, hyperdiverse groups like Arthropoda are vital to monitor in order to understand climate change impacts on biodiversity. This is the first investigation of ground-dwelling arthropod (GDA) assemblages along the full elevation gradient of a mountain range in the Madrean Sky Island Region, establishing a baseline for monitoring future changes in GDA biodiversity. To determine how GDA assemblages relate to elevation, season, abiotic variables, and corresponding biomes, GDA were collected for two weeks in both spring (May) and summer (September) 2011 in the Santa Catalina Mountains, Arizona, using pitfall traps at 66 sites in six distinct upland (non-riparian/non-wet canyon) biomes. Four arthropod taxa: (1) beetles (Coleoptera), (2) spiders (Araneae), (3) grasshoppers and crickets (Orthoptera), and (4) millipedes and centipedes (Myriapoda) were assessed together and separately to determine if there are similar patterns across taxonomic groups. We collected 335 species of GDA: 192/3793 (species/specimens) Coleoptera, 102/1329 Araneae, 25/523 Orthoptera, and 16/697 Myriapoda. GDA assemblages differed among all biomes and between seasons. Fifty-three percent (178 species) and 76% (254 species) of all GDA species were found in only one biome and during only one season, respectively. While composition of arthropod assemblages is tied to biome and season, individual groups do not show fully concordant patterns. Seventeen percent of the GDA species occurred only in the two highest-elevation biomes (Pine and Mixed Conifer Forests). Because these high elevation biomes are most threatened by climate change and they harbor a large percentage of unique arthropod species (11–25% depending on taxon), significant loss in arthropod diversity is likely in the Santa Catalina Mountains and other isolated mountain ranges in the Southwestern US.

Ant communities in native sage scrub, non-native grassland, and suburban habitats in Los Angeles County, USA: conservation implications

Southern California’s sage scrub (SS) ecosystem is severely threatened by suburban development and invasion by non-native grasses, but how these threats impact the arthropod community is poorly understood. Native ants, which face the additional threat of being displaced by non-native Argentine ants, may be particularly at risk of local and regional extirpation. In this study, we surveyed the ant communities in the SS and non-native grassland habitats at the Robert J Bernard Biological Field Station (BFS) and surrounding suburban habitat, and compared patterns of species richness and composition among habitat types. We also compared ant richness and composition at the BFS to 40 coastal SS fragments previously surveyed in San Diego County to better understand how ant communities in interior and coastal SS fragments differ. Ant composition significantly differed among all three habitat types at and surrounding the BFS, but species richness did not. Comparisons between the BFS and coastal fragments indicate that interior SS fragments harbor unique ant species and more species relative to fragment area. Increased richness and unique ant assemblages are probably associated with the limited ability of invasive Argentine ants to colonize the non-native grassland and SS at the BFS. Because many southern California invertebrates are narrowly endemic to low elevation areas, patterns of habitat specificity seen with ants highlight that maintaining a mosaic of SS and non-native grassland habitat, particularly in interior areas where activity and diversity of non-native invertebrate species may be restricted, may be critical to preserving biodiversity.

Two for one: inadvertent introduction of Euglandina species during failed bio-control efforts in Hawaii

The introduction of the predatory land snail, Euglandina rosea (Férrusac, 1821) from Florida to Hawaii to control the giant African snail, Lissachatina fulica (Bowdich, 1822) is among the most publicized biological control cases gone awry. Following preliminary genetic analyses that revealed a second, possibly undescribed Euglandina species was probably introduced to Hawaii, we used an integrative systematic approach combining both genetic and morphological assessments to examine the taxonomic status of the snail referred to as E. rosea in Hawaii. Genetic and morphological analyses support the interpretation that two Euglandina species were introduced to and have become established in Hawaii and can be readily distinguished based on morphological differences. This finding has significant ramifications for understanding both historical and contemporary biocontrol as it suggests that: (1) other species may have been inadvertently introduced through bio-control programs, (2) inadequate understanding of the taxonomy of bio-control agents has obscured our ability to effectively study their ecological impacts, and (3) while the US has no comprehensive regulatory framework for importing biological control agents, one is urgently needed. This also has wide-ranging implications for conservation efforts throughout the tropics because Euglandina from Oahu, Hawaii were released on other Hawaiian Islands, New Guinea, Okinawa, Palau Islands, Philippines, India, Bonin Islands and Bermuda for use in biological control programs that led to catastrophic loss of endemic land snail diversity.

Native Hawaiian Succineids Prefer Non-Native Ginger (Hedychium spp.) Plant Species in the Kohala Mountains, Hawaii: Conservation Ramifications

Abstract: Although non-native species have been implicated as a major factor in the decline of the native Hawaiian land snail fauna, little attention has been focused on understanding how colonization by non-native plants influences Hawaiian land snail populations. The plant preferences of native Hawaiian succineids in the Kohala Forest Reserve were examined where native plant species and invasive non-native ginger species are present to understand how changes in the understory plant composition may influence succineid populations. Surprisingly, native succineid land snails preferred non-native ginger species to native plant species. This finding suggests that native succineid populations may not be negatively affected when the understory plant assemblage changes from a native plant community to one composed primarily of non-native ginger species. However, this preference also indicates that native succineids may be vulnerable to the effects of ginger control efforts. As such, managers should proceed cautiously with ginger removal efforts if they intend not to harm native succineid populations. Hopefully, future efforts to control non-native ginger species will adapt and minimize any negative effects on native succineid species.

Fire Impacts on Ant Assemblages in California Sage Scrub

Abstract. Few studies have examined impacts of fire on invertebrates in southern California ecosystems despite the fact they harbor diverse invertebrate assemblages with many narrowly endemic species. California sage scrub, an endangered ecosystem type of low-elevation areas in southern California, is increasingly threatened by altered fire regimes and type conversion to non-native grasslands often resulting from fire disturbances. The effect of fire on ant assemblages in a patch of recovering sage scrub was examined by using adjacent intact sage scrub and non-native grassland habitats as checks. While short-term effects in ant activity potentially associated with temporary changes in habitat structure and abiotic conditions were observed, ant assemblages in the burned area did not differ between summer 2013 (pre-fire) and fall 2013 (post-fire), or between spring 2013 (pre-fire) and spring 2014 (post-fire). Results indicated that either the ant assemblages recover quickly, or more likely, pre-existing ant assemblage remained and were not directly impacted by fire. Our results, combined with the few other studies that examined impacts of fire on sage scrub invertebrates, are consistent with an emerging hypothesis that ground-dwelling ant/invertebrate assemblages are little affected by direct impacts of fire in semi-arid systems and areas where fires are common.