G. P. Closs

Morphospecies and taxonomic species comparison for Hymenoptera

Abstract The use of morphospecies as surrogates for taxonomic species has been proposed as an alternative to overcome the identification difficulties associated with many invertebrate studies, such as biodiversity surveys. Hymenoptera specimens were collected by beating and pitfall traps, and were separated into morphospecies by a non-specialist with no prior training, and later identified by an expert taxonomist. The number of Hymenoptera morphospecies and taxonomic species was 37 and 42, respectively, representing an underestimation error of 12%. Different families presented varying levels of difficulty, and although the species estimation provided by the use of morphospecies initially appeared to have a relatively minor error rate, this was actually an artefact. Splitting and lumping errors balanced each other out, wrongly suggesting that morphospecies were reasonable surrogates for taxonomic species in the Hymenoptera. The use of morphospecies should be adopted only for selected target groups, which have been assessed as reliable surrogates for taxonomic species beforehand, and some prior training to the non-specialist is likely to be of primary importance.

Invertebrate survey of a modified native shrubland, Brookdale Covenant, Rock and Pillar Range, Otago, New Zealand

Abstract This is the first published invertebrate survey focusing on a low‐altitude shrubland community in New Zealand. Invertebrates were collected from a remnant native shrubland (450 m) protected by the Brookdale Conservation Covenant, Rock and Pillar Range, Otago, New Zealand in late summer/autumn 1999. Sampling was carried out by beating 30 randomly chosen shrubs of each of two native species: Olearia bullata H. D. Wilson & Garnock‐Jones (Asteraceae) and Coprosma propinqua A. Cunn. (Rubiaceae). Fifty pitfall traps were also set under the same shrubs and on nearby open patches of exotic grassland. Three Phyla, six Classes, 25 Orders and approximately 280 species were recorded. An annotated list of taxa is presented, and plant/host associations plus other observations on the fauna are discussed. Approximately 90% of the identified species were endemic, emphasising the importance of such remnant habitats for the protection of New Zealands biodiversity.

Spatial relationships and temporal variability in a littoral macrophyte fish assemblage

The presence of macrophytes in lentic systems often exerts a large influence on the spatial and temporal dynamics of the small-bodied fish that inhabit them, particularly in the presence of piscivorous predators. To examine spatial and temporal patterns of fish abundance in macrophyte stands we sampled fish bimonthly with fine-meshed fish traps by day and night in giant rush habitats of a River Murray billabong between October 1995 and September 1996. Three native and three exotic species were found within these habitats during the study, however, catches were dominated by two species of native carp gudgeons (Hypseleotris spp.). Consistently higher numbers of gudgeons were trapped during the day than at night throughout the study period and there was a sustained decline in catch from spring in the first year to the following spring. The results suggest recruitment of juvenile fish spawned during the summer was insufficient for relative abundance to return to the high numbers found at the start of the study. Fine-scale distribution of carp gudgeons within emergent macrophytes was not generally explained by variability in either physical structure or physicochemical variability. This contrasts with many studies of small fish assemblages in macrophytes where piscivorous predators are present.

Morphological and genetic analysis of Galaxias 'southern' and G. gollumoides: interspecific differentiation and intraspecific structuring

Abstract Morphometrics and amplified fragment length polymorphisms (AFLPs) were used to examine interspecific differentiation and intraspecific variation in two closely related freshwater fishes (Galaxias ’southern’ and G. gollumoides) using sympatric and allopatric populations. The two species were strongly differentiated across all populations, showing 19/24 distinctive morphological features and six fully diagnostic AFLPs. Morphological segregation was principally associated with G. ’southern’ having a larger upper jaw and smaller eye, suggesting that these characters may be useful for field discrimination. No hybridisation was observed between these two fishes, suggesting strong reproductive barriers and supporting species status. Both species showed intraspecific morphological variation among catchments, especially for traits associated with head and mouth morphology. Additionally, G. gollumoides showed intraspecific morphological variation among sites within two streams. Both species showed intraspecific genetic variation among catchments with the same four alleles differing among catchments for both species. Both species showed intraspecific genetic variation among sites within two streams, including consistent variation for the same two alleles. Intraspecific genetic structuring within streams suggests very limited movement among sections of streams. Consistent genetic and morphological variation in the same alleles and traits for both species suggests local adaptation and/or random genetic drift.

Recruitment sources of brown trout identified by otolith trace element signatures

This study examined whether element:Ca ratios within the otoliths of juvenile brown trout could provide accurate trace element signatures for specific natal tributaries, and attempted to match these to trace element natal signatures found within the otoliths of adult trout caught in the main stem rivers of the same catchment. The trace element signatures of juvenile trout otoliths were analysed from a sample of eight tributaries representing the main sub-catchments of the Motueka River catchment, New Zealand. Trace element signatures were determined using laser ablation inductively coupled plasma mass spectrometry, and differentiated using linear discriminant function analysis with an overall cross-validated classification success of 96.8%. Temporal stability in element:Ca ratios was investigated by repeat collections of juvenile fish over two years. Natal signatures from 11 of 23 adult trout sampled from the catchment main stems were matched to one of the eight tributary signatures showing recruitment sources to be spread relatively evenly throughout the catchment. This study demonstrates the potential of using otolith trace element analysis to determine the natal origins of freshwater fish within a catchment.

Life history and reproduction of two abundant mysids (Mysidacea: Mysidae) in an intermittently open New Zealand estuary

Mysids typically form a large proportion of the hyperbenthic faunal biomass in estuaries and are central to the functioning of estuarine food webs. The population dynamics, annual life histories and reproductive effort of two common temperate estuarine mysids, Tenagomysis chiltoni and T. novae-zealandiae, are described in the intermittently open Kaikorai Lagoon, New Zealand. Mysids were sampled by night, monthly from September 2003 to September 2004. Both species completed their life cycles in the lagoon. There was an apparent spatial separation of breeding populations, with T. chiltoni prevalent in the upper lagoon and T. novae-zealandiae dominating the lower lagoon. Densities were lowest in late winter and peaked in late summer/early autumn for both species. Both species exhibited multivoltine life cycles, with breeding peaks occurring in October 2003, December 2003 and February/March 2004 for T. novae-zealandiae, and October/November 2003 and February/March 2004 for T. chiltoni. Breeding strategy for both species varied over the year with the adult size, brood size and the reproductive effort of both T. novae-zealandiae and T. chiltoni all being highest in spring. The life histories of both T. novae-zealandiae and T. chiltoni in the Kaikorai Lagoon are comparable to life histories described for other temperate estuarine mysid species in large open estuaries, and were not significantly modified to cope with the unpredictable demands of life in an intermittent estuary.

Larval drift of amphidromous Gobiomorphus spp. in a New Zealand coastal stream: a critical spatial and temporal window for protection

Amphidromy is a distinct form of diadromy, involving a downstream migration (‘drift’) to a pelagic feeding habitat undertaken by exceptionally small, undeveloped larvae immediately after hatch. Identifying patterns of larval drift may indicate critical periods within which conservation measures can be targeted to protect migrating larvae. This study utilised diel and spatial drift sampling to examine patterns of larval drift in two of New Zealands endemic eleotrid species, the bluegill bully (Gobiomorphus hubbsi) and the common bully (G. cotidianus) in the Waianakarua River, South Island, New Zealand. A distinct spatial and temporal window was identified within which the vast majority of larvae were migrating to sea, extending only a few hours after sunset and < 10u2005km inland. Similar diel patterns of larval drift have been found in other amphidromous species, suggesting this may be a widespread migratory behaviour. Managing water takes to minimise impacts on migrating larvae within this relatively small spatial and temporal window potentially represents a management strategy that could provide safe passage to the vast majority of larval fish while minimising disruption to human activities.

Diel variation in use of cover and feeding activity of a benthic freshwater fish in response to olfactory cues of a diurnal predator

Some fish recognize the threat of predatory fish through chemical cues, which may result in variation in diel activity. However, there is little experimental evidence of diel shifts in activity of prey fish in response to the diel activity of a predator. We compared the total prey consumed and the use of cover by common bullies (Gobiomorphus cotidianus), a native benthic feeding eleotrid, when exposed to the odour of an exotic predator, European perch (Perca fluviatilis), over a 12-h period. Our results showed no significant effect of perch odour on feeding activity, but a significant increase in the use of cover at night and a decrease in the use of cover by day. While common bullies may recognize the presence of a predator through chemical cues, dark conditions may inhibit this and other sensory mechanisms, affecting their ability to recognize the proximity of a predator. For example, during the daytime they may rely on visual cues to initiate cover-seeking behavior, but in the dark, vision is impaired giving them less warning of predators, thus potentially making them more vulnerable.

Late summer hyperbenthic estuarine communities: comparing permanently open and intermittently closed systems along the Otago coastline

Abstract Few studies have compared hyperbenthic communities among estuaries, in either New Zealand or elsewhere. This study presents the results of a single late summer survey of the lower reaches of 26 estuarine systems along the Otago coastline from the Clutha River to Oamaru, comparing hyperbenthic communities among both permanently open and intermittently closed estuaries. Intermittently closed estuaries are periodically closed from the ocean because of the formation of a berm across the mouth. A total of 33 taxa were captured with mysids and amphipods, the most widespread hyperbenthic taxa, being common in both permanently open and intermittently closed Otago estuaries. The mysid, Tenagomysis novae-zealandiae, and amphipod, Paracalliope fluviatilis, were widespread, found in 74% and 68% of all estuaries sampled, respectively. In contrast, most other taxa were present in relatively few estuaries, with 17 species recorded from only 10% of estuaries. There was a significant difference in the community composition among permanently open and intermittently closed estuaries. The results highlight the potential sensitivity of New Zealand estuarine communities to management regimes that may alter their open/closed status.

Does the trace element composition of brown trout Salmo trutta eggs remain unchanged in spawning redds

The temporal stability of trace element concentrations in fertilized, artificially incubated anadromous brown trout Salmo trutta eggs and newly hatched fry was investigated. The anadromous status of the parental fish was confirmed using strontium isotopic analysis of otoliths. Whilst manganese concentrations in eggs varied over time, concentrations of aluminium, potassium, magnesium, strontium, barium and calcium were all unchanged 1 week and 6 weeks post-fertilization as well as in recently hatched larvae. The results clearly suggest that the distinctive trace element signature present in the eggs and newly hatched larvae of anadromous S. trutta (typically characterized by high strontium, low barium) is stable over time. Therefore analysis of the trace element composition of eggs is concluded to be a cost-effective and reliable method for determining the spatial and temporal extent of upstream spawning migration by anadromous salmonids. The temporal variability of at least one element in this study suggests the stability of untested multi-element signatures cannot automatically be assumed.