Jan-Robert Baars

Critical influence of seasonal sampling on the ecological quality assessment of small headwater streams

Variability in the ecological quality assessment of reference sites was tested on small headwater streams in Ireland. Although headwater streams constitute a large portion of the river channel network, they are not routinely monitored for water quality. Various metrics were used including the Irish Q-value and the newly developed Small Streams Risk Score (SSRS), and metrics applied elsewhere in the Atlantic biogeographic region in Europe, including the Biological Monitoring Working Party score (BMWP), the Average Score per Taxon (ASPT), the Ephemeroptera, Plecoptera and Trichoptera taxa (EPT), the Belgium Biotic Index (BBI) and the Danish Stream Fauna Index (DSFI). The AQEM (version 2.5a) assessment software was used to apply some of these metrics. The spring and summer datasets are used to test the performance of biotic metrics with respect to season, and the applicability of their use to assess the ecological quality of wadeable streams. The quality status of most sites assigned by the various metrics was high using the spring invertebrate data, and an apparent considerable deviation in quality status occurred when the summer data was applied. Seasonal differences were noted using all the biotic indices and are attributed to the absence of pollution-sensitive groups in summer. Seasonal variability in the water quality status was particularly evident in acidic streams draining non-calcareous geologies with peaty soils that had relatively lower numbers of taxa. Some indices applied reflect a greater seasonal difference in the quality category assigned. The least amount of variability between seasons was obtained using the ASPT and the SSRS risk assessment system. Results suggest that reference status is reliably reflected in spring when more pollution-sensitive taxa were present, and that a new ecological quality assessment tool is required for application in summer when impacts may be most severe. This highly heterogeneous freshwater habitat seems to have too few taxa present in the summer to reliably determine the ecological quality of the stream using the available indices.

Geographic range, impact, and parasitism of lepidopteran species associated with the invasive weed Lantana camara in South Africa

Abstract The current status of species of Lepidoptera associated with Lantana camara L. (lantana; Verbenaceae) in South Africa was reviewed following a survey aimed at confirming their identity, geographic range, impact on the weed, and parasitism. Six species of Lepidoptera are established on lantana of which two are native, two were probably inadvertently introduced, one was deliberately introduced, and the status of one is unknown. Hypena laceratalis Walker and Characoma submediana Wiltshire (both Noctuidae) are indigenous to South Africa and have extended their host range from native plants to include lantana. Epinotia lantana (Busck) (Tortricidae) and Lantanophaga pusillidactyla (Walker) (Pterophoridae) are exotic species that are presumed to have been inadvertently introduced with the weed. Although three species were deliberately introduced as biological control agents, only Salbia haemorrhoidalis Guenee (Pyralidae) was successfully established. The origin of the serpentine leaf-miner, Aristaea onychota (Meyrick) (Gracillariidae) is still unclear. The moths have mostly established throughout the geographic range of L. camara in South Africa, although S. haemorrhoidalis is restricted to the moist eastern inland and coastal regions. Field populations of all six Lepidoptera species usually occurred at low densities over their established range, but occasionally increased to high densities in localized areas. As a result, the overall impact of these species was usually minimal, and only S. haemorrhoidalis and H. laceratalis were considered to significantly reduce the growth and reproductive rates of lantana. The recovery of several hymenopteran and dipteran parasitoid species from the Lepidoptera species surveyed suggests that a high incidence of parasitism may be the major factor limiting population increases of most of the moth species. This study supports the contention that additional agents are required to supplement the biological control of L. camara in South Africa.

Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in Europe

The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.

Biology, host range, and risk assessment supporting release in Africa of Falconia intermedia (Heteroptera: Miridae), a new biocontrol agent for Lantana camara

Abstract The ornamental hybrid shrub, Lantana camara L. (lantana), is a serious environmental weed and has been targeted for biological control in South Africa since 1961. The established biocontrol agents cause insufficient levels of damage and additional natural enemies are required to reduce the invasiveness of this weed. The lantana mirid, Falconia intermedia (Distant), is a promising new agent that was imported from the Caribbean for life history and host-range studies. The nymphs and adults are leaf-suckers that cause chlorotic speckling, which reduces the photosynthetic capacity of the plant. Biological studies indicate that F. intermedia has considerable biocontrol potential, in that it has a high intrinsic rate of increase, the potential for multiple generations a year, highly mobile adults, and a high level of damage per individual. Host-specificity trials indicated that the lantana mirid has a narrow host range, with L. camara being the most suitable host, but several indigenous African species in the closely related genus Lippia are suitable alternative host plants. Under multiple-choice conditions, adults showed a significant and strong oviposition preference for L. camara over the Lippia species. A risk assessment of potential nontarget effects indicated that three Lippia species could sustain damage levels in the field. The relatively low probability of damage to indigenous species was considered a justified trade-off for the potentially marked impact on L. camara. The regulatory authorities accepted the results of this study and F. intermedia was released against L. camara in South Africa in April 1999.

Optimising sample volume and replicates using the Bou-Rouch method for the rapid assessment of hyporheic fauna

Despite the widespread use of the Bou-Rouch method in obtaining hyporheic samples in ecological studies, problems persist in comparing data because of differences in volume and number of samples taken in various studies. Towards standardising this method, we conducted a study in the Delour River, Ireland, between March and September 2006. The hyporheic habitat was divided into three lateral zones: the flowing stream (SS); the stream–terrestrial ecotone (EC); and the terrestrial margin (TM). Between 3 and 6 random insertions of the stand pipe were made into the hyporheic habitat at 0.2 m and 0.5 m in each zone. Ten consecutive 1-L samples were pumped at each point to determine an optimum sample volume and replicates needed to estimate taxon richness and abundance. The optimum sample combinations range between 6 and 15 3- to 10-L samples depending on depth and habitat zone. Our results show that both spatial and temporal scales are important factors in considering the optimum combinations of sample volume and number of independent spatial replicates needed to sample stream hyporheos, with the zone closer to the flowing stream requiring many small-volume samples whereas areas further away towards the alluvial groundwater need larger volumes with small numbers of replicates.

Comparison of macroinvertebrate community structure and driving environmental factors in natural and wastewater treatment ponds

Eutrophication still continues to be an issue of major concern for the protection of water quality, and accordingly, the European Union Water Framework Directive has set a minimum target for all waters where “good status” is defined as a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact. The use of constructed ponds for wastewater treatment aimed at achieving this target has shown to be an effective alternative to conventional systems in the farm landscape. Their applicability in these areas is of great interest since these ponds have the added potential to combine their wastewater treatment properties with that of biodiversity enhancement. This article focuses on exploring the community structure of both natural and constructed ponds used for wastewater treatment and the driving environmental factors. A total of 15 constructed and 5 natural ponds were sampled for aquatic macroinvertebrates and hydrochemistry in spring and summer 2006. Results showed that the most important factors responsible for the differences in the community structure between these two types of ponds were pH, vegetation structure and pollution levels. These gradients helped to structure a large proportion of the communities with some taxa being associated with the constructed ponds. These results highlight the potential contribution of constructed ponds used for wastewater treatment to the landscape biodiversity. The present findings also open the possibility for a more integrated management of water quality and biodiversity enhancement in farmland areas.

Biology and host range of Aconophora compressa, a candidate considered as a biocontrol agent of Lantana camara in Africa

The shrub, Lantana camara L. (Verbenaceae), of tropical American origin, is a serious weed in South Africa and is the target of a biological control programme. The stem-sucking membracid, Aconophora compressa Walker (Homoptera: Membracidae), from Mexico was reported to be very damaging and was therefore imported into South Africa for biology and host range studies. The female partially inserts the eggs into the woody portion of actively growing stems, and guards them against potential predators. Nymphs develop through five instars to the adult stage in about 45 days. The adults and nymphs feed on the sap of stems causing the leaves to wilt, the flowers to abort and the gradual dieback of stems. No-choice experiments showed that adult survival, egg production, and nymphal emergence was high on L. camara, and also on related ornamental and indigenous species. The adult reproductive performance was higher on some indigenous Lippia species than on L. camara. Furthermore, the nymphs developed faster on these indigenous species and high rates of reproductive performance on these non-target species were sustained over several generations. In multiple-choice trials, equal or larger numbers of egg batches were recorded from indigenous Lippia species and the ornamental plant, Aloysia citrodora Palau, than on L. camara. The treehopper, A. compressa, poses an unacceptable threat to indigenous Lippia species and has therefore been rejected as a biocontrol agent for L. camara in Africa.

The life history of Perla bipunctata Pictet, 1833 (Plecoptera: Perlidae) in the upper River Liffey, Ireland

Perla bipunctata is the most common species of Perlidae in Ireland occurring in fast flowing, clean rivers and small streams. Although a common component of freshwater biological studies, little is known about the autecology of this stonefly. Monthly kick and Surber samples were taken over a 1-year period in the upper reaches of the River Liffey (4th order) to determine the life history of larvae. Perla bipunctata has a merovoltine life cycle taking no less than three years to complete the immature stages. Life history plots suggest two periods of egg hatching, followed by two separate cohorts developing over different lengths of time. Mature larvae from both cohorts synchronise and emerge as adults over a short period in early summer. The merovoltine life cycles of long lived invertebrates like P. bipunctata emphasise the importance of such species in reflecting the ecological quality of freshwaters over a long period of time.

Biology of the Eucalyptus leaf beetle Paropsisterna selmani (Chrysomelidae: Paropsini): a new pest of Eucalyptus species (Myrtaceae) in Ireland

The biology of the Eucalyptus leaf beetle Paropsisterna selmani (de Little) (Chrysomelidae: Paropsini) was assessed in the field and under laboratory conditions. The invasive species, most probably from Tasmania, severely defoliates the new flush foliage of several Eucalyptus species in Ireland. The adult beetles and larvae both fed on the foliage and caused typical broom‐top damage to trees. Adult beetles over‐wintered in the soil and emerged in April and laid egg batches of approximately seven eggs on the leaves. Teneral adults were most noticeable in late June and July. In bioassays, the life cycle took approximately 26 days to complete at 20 °C, and survival rates were approximately 67% when fed on E. parvula. Teneral adults took 13.3 days to initiate egg‐laying. Leaf consumption was highest in female larvae, and adult beetles consumed a leaf area of approximately 102 mm2/day. A mean daily egg‐laying rate of 11.4 eggs/female was recorded over a period of 130 days. This egg‐laying rate is comparable to other leaf beetles attaining pest status in other Eucalyptus‐growing regions. The biology of Pt. selmani suggests that this will be a significant pest of Eucalyptus species grown for cut‐foliage and forestry in Ireland. It also poses a potential threat to eucalypt‐growing regions in the U.K. and mainland Europe.

Macroinvertebrate diversity in constructed ponds: community structure and driving environmental factors

Ponds in various parts of Europe have been shown to make a significant contribution to regional diversity (BRONMARK & HANSSON 2002, ÜERTLI et al. 2005) and can support more unique an d more rare species than other waterbody types (WrLLIAMS et al. 2003). A number of studies have emphasized the importance o f creating an d maintaining a variety o f pond types to maximise gamma biodiversity, drawing special attention to environmental factors such as water permanence ( e.g., BIGGS et al. 1994). Despite this, little research has been conducted on the environmenta1 factors that structure and promote macroinvertebrate diversity in ponds. Broos et al. (1994) suggested that seasonal ponds cou1d host rare species not found in other aquatic habitats. In addition, GEE et al. (1997) indicated that 2 small ponds supported more species together than a sing1e larger pond of similar area. Biotic factors also appear to be important; FAIRCHILD et al. (2000) showed that fish in ponds variably affected the number of anisopteran and trichopteran species. Considerably less is known about the macroinvertebrate communities or the environmental factors controlling biodiversity in ponds constructed for effluent treatment. In fact, only 3 studies have explored the macroinvertebrate communities in constructed wetlands and the relationships between these and environmental factors (FAIRCHILD et al. 2000, SPIELES & MnscH 2000, BALCOMBE et al. 2005). W e explored the environmental factors structuring the macroinvertebrate community composition of Integrated Constructed Wetlands (ICWs) from the Anne Valley, Co. Waterford, Ireland (E250600; Nl03750). These results may contribute to the implementation of good design principles to promote biodiversity in future pond creation.