Rocks and clocks: linking geologic history and rates of genetic differentiation in anchialine organisms

The geologic history of a region can significantly impact the development of its flora and fauna, with past events shaping community patterns and evolutionary trajectories of species. In this context, islands are excellent “natural laboratories” for studying the fundamental processes of evolution due to their discrete geographical nature and dynamic geologic histories. An island system meeting these criteria is the Hawaiian Archipelago, which is ideal for testing how island geologic history influences the processes leading to population genetic variation and differentiation. One Hawaiian endemic whose evolutionary history is closely tied to the geology of the islands is the anchialine atyid shrimp Halocaridina, whose mitochondrial cytochrome oxidase I (COI) gene is hypothesized to be evolving at the rate of 20% per million years. To validate this rapid evolutionary rate, time since divergence estimates between geographically close, yet genetically distinct, populations were calculated for Halocaridina from anchialine habitats on the islands of Hawai’i, Maui, and O’ahu. On the younger (i.e., <1.5 million years) islands of Hawai’i and Maui, where all anchialine habitats occur in basalt, application of the Halocaridina molecular clock identified a strong correlation between levels of genetic divergence and the geologic age of the region inhabited by those populations. In contrast, this relationship weakened when similar analyses were conducted for Halocaridina from limestone anchialine habitats on the older (i.e., >2.75 million years) island of O’ahu. These results suggest geologic age, basin origin and/or composition are important factors that should be taken into consideration when conducting molecular clock analyses on anchialine flora and fauna as well as island populations in general.     

How might sea level change affect arthropod biodiversity in anchialine caves: a comparison of Remipedia and Atyidae taxa (Arthropoda: Altocrustacea)

Sea level change influences biodiversity of endemic cave fauna to varying degrees. In anchialine systems, a marine layer flows under less saline layers, each with differing associated fauna. We assess the role of present and historic (last glacial maximum – 18,000 years ago) distance from the ocean in determining species richness and phylogenetic diversity patterns for two groups of anchialine crustaceans: the marine-restricted Remipedia and a subset of groundwater-inhabiting atyid shrimp with greater tolerance for salinity variation. We calculated species richness and phylogenetic diversity per cave based on records of remipede and atyid diversity at 137 locations in the Yucatán Peninsula, Caribbean, Australia, and the Canary Islands. After calculating the distance of each cave’s surface opening from the past and present shoreline, we evaluated how species richness and phylogenetic diversity change with distance from the present and historic ocean. Remipede species richness and phylogenetic diversity declined rapidly with distance from the ocean. Ninety-five percent of the remipedes surveyed were located within 7 km of the present ocean and 18 km of the historic ocean. Atyid species richness and phylogenetic diversity declined more slowly with distance from the ocean than that of remipedes. Atyid shrimp were also distributed over a broader range: 95 % were located within 100 km of the present ocean and 240 km of the historic ocean. Our findings indicate that coastal geomorphology and salinity tolerance influence a clade’s distribution with respect to its distance from the ocean. We also report a possible latent response to sea level change.     

Predator-dependent diel migration by <Emphasis Type="Italic">Halocaridina rubra</Emphasis> shrimp (Malacostraca: Atyidae) in Hawaiian anchialine pools

Diel migration is a common predator avoidance mechanism commonly found in temperate water bodies and increasingly in tropical systems. Previous research with only single day and night samples suggested that the endemic shrimp, Halocaridina rubra, may exhibit diel migration in Hawaiian anchialine pools to avoid predation by introduced mosquito fish, Gambusia affinis, and perhaps reverse migration to avoid the predatory invasive Tahitian prawn, Macrobrachium lar. To examine this phenomenon in greater detail, we conducted a diel study of H. rubra relative abundance and size at 2-h intervals in three anchialine pools that varied in predation regime on the Kona-Kohala Coast of Hawai‘i Island. We found two distinct patterns of diel migration. In two pools dominated by visually feeding G. affinis, the abundance of H. rubra present on the pool bottom or swimming in the water column was very low during the day, increased markedly at sunset and remained high until dawn. In contrast, in a pool dominated by the nocturnal predator M. lar, H. rubra density was significantly lower during the night than during the day (i.e., a pattern opposite to that of shrimp in pools containing fish). In addition, we observed that the mean body size of the shrimp populations varied among pools depending upon predator type and abundance, but did not vary between day and night in any pools. Our results are consistent with the hypothesis that H. rubra diel migratory behavior and size distributions are influenced by predation regime and suggest that diel migration may be a flexible strategy for predator avoidance in tropical pools where it may be a significant adaptive response of endemic species to introduced predators.     

Density‐ and trait‐mediated top–down effects modify bottom–up control of a highly endemic tropical aquatic food web

Benthic invertebrates mediate bottom–up and top–down influences in aquatic food webs, and changes in the abundance or traits of invertebrates can alter the strength of top–down effects. Studies assessing the role of invertebrate abundance and behavior as controls on food web structure are rare at the whole ecosystem scale. Here we use a comparative approach to investigate bottom–up and top–down influences on whole anchialine pond ecosystems in coastal Hawai‘i. In these ponds, a single species of endemic atyid shrimp (Halocaridina rubra) is believed to structure epilithon communities. Many Hawaiian anchialine ponds and their endemic fauna, however, have been greatly altered by bottom–up (increased nutrient enrichment) and top–down (introduced fish predators) disturbances from human development. We present the results of a survey of dissolved nutrient concentrations, epilithon biomass and composition, and H. rubra abundance and behavior in anchialine ponds with and without invasive predatory fish along a nutrient concentration gradient on the North Kona coast of Hawai‘i. We use linear models to assess 1) the effects of nutrient loading and fish introductions on pond food web structure and 2) the role of shrimp density and behavior in effecting that change. We find evidence for bottom–up food web control, in that nutrients were associated with increased epilithon biomass, autotrophy and nutrient content as well as increased abundance and size of H. rubra. We also find evidence for top–down control, as ponds with invasive predatory fish had higher epilithon biomass, productivity, and nutrient content. Top–down effects were transmitted by both altered H. rubra abundance, which changed the biomass of epilithon, and H. rubra behavior, which changed the composition of the epilithon. Our study extends experimental findings on bottom–up and top–down control to the whole ecosystem scale and finds evidence for qualitatively different effects of trait‐ and density‐mediated change in top–down influences.     

Diurnal dynamics of the microbial loop in peatlands: structure, function and relationship to environmental parameters

Globally, introductions of alien species are increasingly common, with invasive predators potentially having detrimental effects via predation on native species. However, native prey may avoid predation by adopting new behaviors. To determine whether invasive fish populations consume endemic shrimp in invaded Hawaiian anchialine habitats or if adopted patterns of diel migration prevents predation as previously hypothesized, a total of 183 invasive poeciliids (158 Gambusia affinis and 25 Poecilia reticulata) were collected for gut content analyses from four anchialine sites during wet and dry seasons on the islands of Hawai‘i and Maui. Predation on shrimp was not detected in habitats where they retreat exclusively into the underlying aquifer diurnally and only emerge nocturnally. However, low levels of predation were detected (7/65 fishes, only by Gambusia affinis) at Waianapanapa Cave, Maui, where shrimp retreat into both the aquifer and a cave during the day. Thus, adopted behavioral responses to invasive fishes generally, though not universally, prevent predation on endemic Hawaiian anchialine shrimps. However, non-consumptive effects resulting from behavioral modification of shrimps may have appreciable impacts on the Hawaiian anchialine ecosystem and warrant further study.     

Patterns of genetic connectivity among anchialine habitats: a case study of the endemic Hawaiian shrimp Halocaridina rubra on the island of Hawaii

Anchialine habitats, landlocked bodies of mixohaline water that fluctuate with the tides but have no surface connection to the sea, are known from around the world. Many anchialine organisms have widespread distributions and it has been hypothesized that high levels of gene flow and low levels of genetic differentiation are characteristic of populations from these habitats. However, the generality of this hypothesis requires further assessment, particularly in light of the significant negative impact these habitats and their biota have experienced from anthropogenic causes. This study investigated the population structure and demography of an endemic Hawaiian anchialine species, the atyid shrimp Halocaridina rubra, using mitochondrial cytochrome c oxidase subunit I (COI) gene sequences. A survey of 305 individuals from 16 populations collected on the island of Hawaii revealed 135 haplotypes. These haplotypes belonged to one of two divergent (2.7-4.9%) lineages; notably, no haplotypes were shared between the two coasts of the island. Along each coast, strong subdivision and little to no gene flow occurs between populations separated by > 30 km. The population structure and demography of H. rubra on Hawaii are influenced by regional hydrology, geology, volcanism and two distinct colonization events of the island. Thus, H. rubra on Hawaii demonstrates that populations of endemic anchialine organisms may exhibit significant levels of genetic structure and restricted levels of gene flow over limited geographic scales. This report brings novel insight into the biology of anchialine organisms and has important implications for the future management of these habitats and their biota.     

Impact of groundwater salinity on vegetation species richness in the coastal pine forests and wetlands of Ravenna,Italy

In the coastal pine forests (Pinus pinea and Pinus pinaster) of Ravenna (Italy) along the Adriatic coast, many pine trees are stressed or dying. In this paper we present ground elevation, depth to watertable, salinity of groundwater and vegetation species richness data within one of the coastal pine forests and some wetlands north of the Bevano River between LAT. 44°23′10″ and LAT. 44°20′21″ and between LONG. 12°17′25″ and LONG. 12°19′33″. The data are presented areally and along a 50 m long transect perpendicular to the coast to study the cause of distress in the pine forest and in different water pools within the wetlands. The findings were compared to published values of tolerance to salinity for 39 plant species typical of the area and incorporated into a web application to help nature managers in assessing or adjusting water salinity in relation to the vegetation species present. The pine trees are relatively tolerant to salinity (up to 12 g/l) but cannot survive a shallow watertable. On the other hand, species richness or biodiversity in this area is promoted by a shallow watertable and low salinity.     

Hawaiian biogeography and the islands' freshwater fish fauna

Aim This paper describes known patterns in the distributions and relationships of Hawaiian freshwater fishes, and compares these patterns with those exhibited by Hawaii's terrestrial biota. Location The study is based in Hawaii, and seeks patterns across the tropical and subtropical Indo‐west Pacific. Methods The study is based primarily on literature analysis. Results The Hawaiian freshwater fish fauna comprises five species of goby in five different genera (Gobiidae). Four species are Hawaiian endemics, the fifth shared with islands in the western tropical Pacific Ocean. All genera are represented widely across the Indo‐west Pacific. All five species are present on all of the major Hawaiian islands. All five species are amphidromous – their larval and early juvenile life being spent in the sea. Although there has been some local phyletic evolution to produce Hawaiian endemics, there has been no local radiation to produce single‐island endemics across the archipelago. Nor is there evidence for genetic structuring among populations in the various islands. Main conclusions In this regard, the freshwater fish fauna of Hawaii differs from the well‐known patterns of local evolution and radiation in Hawaiian Island terrestrial taxa. Amphidromy probably explains the biogeographical idiosyncrasies of the fish fauna – dispersal through the sea initially brought the fish species to Hawaii, and gene flow among populations, across the archipelago, has hitherto inhibited the evolution of local island endemics, apparently even retarding genetic structuring on individual islands.     

In-stream behaviour of threatened fishes and their food organisms based on remote video monitoring

Can remote underwater video be used to investigate the in-stream behaviour of small fishes and decapods? Diel activity of two threatened freshwater fishes (Macquaria australasica and Gadopsis bispinosus), a palaemonid prawn and an atyid shrimp, was established from remote underwater video in a pool of an upland stream in the current study. Decapods and large fishes (>5 cm TL) were nocturnal, whereas, small fishes (<5 cm TL) were diurnal. The suitability of using underwater video to quantify short-term (seconds) behavioural interaction among individuals was also demonstrated, with early-juvenile-phase Gadopsis bispinosus exhibiting interference competition on 35% of occasions when two or more individuals were observed. This study demonstrates that remote underwater video is useful for observing the in-stream behaviour of threatened freshwater fauna where other techniques are not viable, and presents sub-sampling of video as a means of reducing video processing time in assessing fish diel activity patterns.     

Combining otolith chemistry and telemetry to assess diadromous migration in pinkeye mullet, <Emphasis Type="Italic">Trachystoma petardi</Emphasis> (Actinopterygii,Mugiliformes)

Little is currently known regarding microbial community structure, and the environmental factors influencing it, within the anchialine ecosystem, defined as near-shore, land-locked water bodies with subsurface connections to the ocean and groundwater aquifer. The Hawaiian Archipelago is home to numerous anchialine habitats, with some on the islands of Maui and Hawaii harboring unique, laminated orange cyanobacterial–bacterial crusts that independently assembled in relatively young basalt fields. Here, benthic and water column bacterial and micro-eukaryotic communities from nine anchialine habitats on Oahu, Maui, and Hawaii were surveyed using high-throughput amplicon sequencing of the V6 (Bacteria-specific) and V9 (Eukarya-biased) hypervariable regions of the 16S- and 18S-rDNA genes, respectively. While benthic communities from habitats with cyanobacterial–bacterial crusts were more similar to each other than to ones lacking it on the same island, each habitat had distinct benthic and water column microbial communities. Analyses of the survey data in the context of environmental factors identified salinity, site, aquifer, and watershed as having the highest explanatory power for the observed variation in microbial diversity and community structure, with lesser drivers being annual rainfall, longitude, ammonium, and dissolved organic carbon. Our results epitomize the abiotic and biotic uniqueness characteristic of individual habitats comprising the Hawaiian anchialine ecosystem.     

Life history features of some macroinvertebrates in a French Polynesian stream

The invertebrate fauna of the Opunohu River catchment in Moorea, French Polynesia, studied 1988–1989, was numerically dominated by four species of neritid snails, one species of thiarid snail, two species of atyid shrimp, two species of palaemonid shrimp, and ten species of coenagrionid, chironomid, and simuliid insect larvae. Numbers of egg capsules of neritid snails were higher in riffles (maximum x density > 10,000/m² surface area) than pools, were highest in riffles in September and pools in August, and were lowest in both habitats in March and December. The snail Neritina canalis Lamarck and the shrimp Atyoida pilipes Newport, Caridina weberi DeMan, Macrobrachium lar Fabricius, and Macrobrachium australe Guerin‐Menévílle are diadromous: they enter freshwater as juveniles and migrate upstream; their larval offspring return to the ocean for growth and development. Ovigerous females of A. pilipes and M. lar were mainly found in austral fall; ovigerous females of C. weberi and M. australe were found in both austral fall and spring. Ovigerous females were the largest individuals of each shrimp species collected. Mean size of N. canalis, A. pilipes, C. weberi, and M. lar was generally larger in upstream than downstream reaches; no such difference was found for the non‐diadromous thiarid snail Melanoides tuberculata Müller. Coenagrionid, chironomid, and simuliid insect larvae have multiple cohort populations but at least one simuliid species occurs as a single cohort. Downstream habitat alteration may strongly influence the distribution of diadromous species.     

Seasonal and interannual variation in distribution and population abundance of the shrimp Crangon franciscorum in San Francisco Bay

Shrimp are an important component of the San Francisco Bay biota, both as predators on benthic fauna, and as a food source for predatory fish. Of three common species in the bay, Crangon franciscorum is the most abundant. The bay is predominantly a nursery area for maturing shrimp of this species. During the main reproductive period in the early spring, ovigerous females and planktonic larvae are in most years centered outside the bay in the nearshore ocean, although both are also present in the bay. Juveniles move into both the southern reach and the northern reach shortly after settling, and landward-flowing bottom currents are possibly instrumental in this migration. The seasonal cycle of shrimp abundance in the bay, dominated by this spring immigration of newly settled juveniles, is characterized by a progressive migration of the growing shrimp up the estuary coincident with upstream penetration of higher salinity water during summer. Differences in abundance and distribution between the years 1980, 1981, and 1982 suggest that the level of river discharge and accompanying salinity regime are important controlling factors in the distribution, recruitment levels, and subsequent survival and growth of C. franciscorum in the San Francisco Bay.     

Effect of environmental factors on the structure and functioning of biocoenoses of hyperhaline water reservoirs in the south of Western Siberia

Based on the perennial monitoring (1995–2010) of hyperhaline water reservoirs in the south of Western Siberia with salinity from 28 to 417 g/L, four seasons in the development of biocoenoses are distinguished and integrated results of studies of the effect of environmental factors on the species composition and productivity of biocoenoses are presented. The decisive role of temperature on the seasonal cycles of hydrocole development and salinity on the productivity and composition of biocoenoses are revealed. The highest species diversity is observed in summer at temperatures above 12°C; the fauna is represented only by artemia cysts at negative temperatures. With an increase of salinity from 28 to 100 g/L the number of species declines. For salinity 100 g/L the fauna is represented only by brine shrimp Artemia. Hyperhaline biocoenoses are the most productive at salinity 150–180 g/L.     

Phylogeny and historical biogeography of the cave-adapted shrimp genus Typhlatya (Atyidae) in the Caribbean Sea and western Atlantic

Aim To infer phylogenetic relationships among five species of the cave‐adapted shrimp genus Typhlatya in order to test competing hypotheses of dispersal and colonization of the disjunct cave localities occupied by these five species. Location Typhlatya species are found in caves and anchialine ponds across the northern margin of the Caribbean Sea, along the Mediterranean and Adriatic coasts and on oceanic islands in the Atlantic and eastern Pacific oceans. This study focuses on five species, one from Bermuda, one from the Caicos Islands and three from the Yucatan Peninsula of Mexico. Methods Partial sequences (c. 1400 bp) from the mitochondrial cytochrome b, 16S rDNA and COI genes were obtained from representative samples of the five species. Phylogenetic inference was carried out with maximum parsimony and maximum likelihood analyses. Parsimony networks were constructed for the Bermudian species Typhlatya iliffei and one Yucatan species Typhlatya mitchelli, to determine the degree of connectivity among populations inhabiting different cave systems. Results All three land masses were recovered as monophyletic. The two insular marine species from Bermuda and the Caicos Islands formed a clade, while the three continental freshwater species from the Yucatan Peninsula formed another. Within both Bermuda and the Yucatan, shared haplotypes were found in different cave systems, suggesting recent or ongoing gene flow among populations in both locales. Main conclusions The two insular marine Typhlatya species originated from an ancestral marine population, possibly already cave‐adapted, that is suggested to have colonized the Caicos Islands and subsequently dispersed to Bermuda via the Gulf Stream. Divergence estimates suggest that colonization occurred before the formation of present‐day anchialine cave habitat, which did not form on either island until the late Pliocene to early Pleistocene. Divergence estimates also indicate that the Yucatan freshwater species split before the formation of freshwater cave habitat in the Yucatan. These species could have inhabited crevicular marine habitats before the late Pliocene/early Pleistocene in the Yucatan or elsewhere in the Caribbean, and subsequently migrated to freshwater caves once they formed.     

Atyid shrimps (Decapoda: Atyidae) influence the spatial heterogeneity of algal communities over different scales in tropical montane streams, Puerto Rico

1. Atyid (Decapoda: Atyidae) shrimps influence the distribution of algal communities over different scales in tropical montane streams of Puerto Rico. Within pools of an atyid-dominated stream, atyid shrimps enhanced patchiness in algal communities along the depth gradient. Algal bands occurred in shallow pool margins where atyids did not forage (< 3 cm below water surface), with significantly greater standing crop, taxon richness, and structural complexity than deeper areas. In deeper water, atyids reduced small-scale patchiness in algal community composition and maintained a low-growing understorey turf dominated by sessile diatoms (Bacillariophyta) and, sometimes, closely cropped, filamentous blue-greens (Cyanophyta).
2. Among pools of the atyid-dominated stream, atyids interacted with light to determine algal patchiness between stream margins and deeper areas. In sunny pools, algal standing crop was 140-fold greater in pool margins than in deeper areas where atyids foraged. In shaded pools, however, standing crop in pool margins was only 5-fold greater than in deeper areas. Effects of light on algal standing crop were greater outside atyid foraging areas than within, indicating that shrimp grazing overrides the positive effects of light.
3. In contrast to the atyid-dominated stream, algal communities in an atyid-poor stream were characterized by a high biomass of loosely attached epipelic diatoms and no depth zonation. Interstream rock and shrimp transplant experiments indicated that atyids significantly reduced algal standing crop and altered community composition on rocks from atyid-poor streams within 24 h. Results support the hypothesis that atyid shrimps play a major role in determining observed interstream differences in algal communities.     

Effects of the Tropical Freshwater Shrimp Caridina weberi (Atyidae) on Leaf Litter Decomposition1

Effects of feeding by atyid shrimp, Caridina weberi, on the rate of decomposition of leaf litter were studied in the Opunohu River, Moorea, French Polynesia. In a laboratory feeding experiment shrimp consumed microbially conditioned Hibiscus leaves, but in a field study shrimp did not affect the rate of decomposition of leaf litter. In this system, the rate of decomposition was influenced more by water discharge or by microbial activity than by shrimp.     

Life cycle of Boeckella poppei Mrazek and Branchinecta gaini Daday (King George Island, South Shetlands)

In Lake Wujka, a shallow, polymictic Antarctic lake situated at 15 m from the seashore, several yearly cohorts occur of the copepod Boeckella poppei and one of the fairy shrimp Branchinecta gaini. There is circumstantial evidence that the two species compete for food, and perhaps adult fairy shrimp feed on the nauplii of the copepod. Both species are positively influenced by a measure of salinity. However, when autumn storms massively sweep seawater into the lake, all fairy shrimp are wiped out; no hatching occurs until next spring. In B. poppei, some nauplii and copepodites survive or hatch after the salt flows out of the lake. This is an advantage to the copepod that may balance its coexistence with the shrimp. Its cycle is, however, aborted by the freezing of the lake. In contrast to many other Antarctic lakes, the life cycle of the crustaceans is therefore controlled by salinity rather than freezing.     

An island in the stream: Australia's place in the cosmopolitan world of Indo-West Pacific freshwater shrimp (Decapoda: Atyidae: Caridina)

Mitochondrial DNA sequences were used to investigate phylogenetic and biogeographic relationships among Australian freshwater shrimp from the genus Caridina H. Milne Edwards, 1837 (Atyidae) and congeners from potential source populations throughout the Indo-West Pacific region. Numerous Australian taxa have close evolutionary relationships with non-Australian taxa from locations throughout the region, indicating a diverse origin of the Australian freshwater fauna. This implies many colonisations to or from Australia over a long period, and thus highlights the surprising adeptness of freshwater shrimp in dispersal across ocean barriers and the unity of much of the region's freshwater biota. Interestingly, a study on Australia's other main genus of atyid shrimp, Paratya Miers, 1882, inferred only a single colonisation. A number of potential species radiations within Australia were also identified. This agrees with patterns detected for a large number of Australian freshwater taxa, and so implies a vicariant explanation due to the development of colder, dryer climates during the late Miocene/early Pliocene.     

Effects of omnivorous shrimp in a montane tropical stream: sediment removal,disturbance of sessile invertebrates and enhancement of understory algal biomass

Freshwater shrimp dominate the faunal biomass of many headwater tropical streams: however, their role in community organization is unclear. Enclosure/exclosure experiments in a montane Puerto Rican stream examined direct and indirect effects of two dominant taxa of atyid (Atyidae) shrimp, Atya lanipes Holthuis and Xiphocaris elongata Guerin-Meneville. Both shrimp taxa caused significant reductions in sediment cover on rock substrata, reducing sedimentation and enhancing algal biovolume on clay tiles in cages. When tiles incubated in shrimp exclosures for 2 wks were placed outside of cages, atyid shrimp removed 100% of the sediment cover within a 30 min observation period. Atyid shrimp appear to play an important role in stream recovery after high discharge events by rapidly removing sediments and detritus deposited on benthic substrata in pools. We evaluated the mechanism by which A. lanipes influences algae and benthic insects by comparing patterns of algal biomass, taxonomic composition, and insect abundance between shrimp-exclusion and shrimp-presence treatments both with and without manual sediment removal. The shrimp exclusion treatment without manual sediment removal bad significantly lower algal biomass and greater sedimentation than all other treatments. The treatment in which shrimp were excluded but sediment was manually removed, however, accrued almost the same algal biovolume as the shrimp enclosure treatment, supporting the hypothesis that sediment removal enhances the biovolume of understory algal taxa. Algal community composition was similar between stream bottom bedrock exposed to natural densities of shrimp and all experimental treatments for both Atya and Xiphocaris: a diatom community strongly dominated (78–95%) by the adnate taxon, Achnanthes lanceolata Breb ex. Kutz. Atyid shrimp are important in determining the distribution and abundance of benthic insects through both direct and indirect effects. Sessile, retreat-building chironomid larvae (Chironomidae: Diptera) are negatively affected by both A. lanipes and X. elongata, through direct removal by foraging activities and/or indirectly through depression of sediment resources available to larvae for the construction of retreats. In constrast, the mobile grazer, Cloeodes maculipes (Baetidae: Ephemeroptera) was not adversely affected and atyid shrimp have the potential to exert positive indirect effects on this taxon by facilitating its exploitation of algal resources and/or through enhancement of understory algal food resources through sediment removal.     

Alien dominance of the parasitoid wasp community along an elevation gradient on Hawai’i Island

Through intentional and accidental introduction, more than 100 species of alien Ichneumonidae and Braconidae (Hymenoptera) have become established in the Hawaiian Islands. The extent to which these parasitoid wasps have penetrated native wet forests was investigated over a 1,765 m elevation gradient on windward Hawai’i Island. For >1 year, malaise traps were used to continuously monitor parasitoid abundance and species richness in nine sites over three elevations. A total of 18,996 individuals from 16 subfamilies were collected. Overall, the fauna was dominated by aliens, with 44 of 58 species foreign to the Hawaiian Islands. Ichneumonidae was dominant over Braconidae in terms of both diversity and abundance, comprising 67.5% of individuals and 69.0% of species collected. Parasitoid abundance and species richness varied significantly with elevation: abundance was greater at mid and high elevations compared to low elevation while species richness increased with increasing elevation, with all three elevations differing significantly from each other. Nine species purposely introduced to control pest insects were found, but one braconid, Meteorus laphygmae, comprised 98.0% of this assemblage, or 28.3% of the entire fauna. Endemic species, primarily within the genera Spolas and Enicospilus, were collected almost exclusively at mid- and high-elevation sites, where they made up 22.1% and 36.0% of the total catch, respectively. Overall, 75.9% of species and 96.0% of individuals are inferred to parasitize Lepidoptera larvae and pupae. Our results support previous data indicating that alien parasitoids have deeply penetrated native forest habitats and may have substantial impacts on Hawaiian ecosystems.