Gianmaria Carchini

Performance of different biotic indices and sampling methods in assessing water quality in the lowland stretch of the Tiber River

The lowland stretches of rivers are usually the ones where a macroinvertebrate species collection is more difficult to obtain because of the depth and turbidity of the water. Since the choice of the index and of the specific sampling technique is critical for the final result, there is a strong interest into setting up reliable methods for assessing the biological water quality. The aim of this paper is to elucidate the performances of four biotic indices and the influence of four sampling methods on the water quality assessment of a deep and turbid stretch of a river. We collected macroinvertebrates seasonally at 10 sampling sites along the final stretch of the Tiber River using four sampling methods (including hand net, wood and plastic artificial substrates). At the same time, chemical, physical, and bacteriological variables were recorded monthly along the same river stretch. Considering those variables, sampling sites were grouped into three clusters with different water quality, using the chronological clustering method. The same result was obtained from macroinvertebrate data using the same method. We then examined the ability of four biotic indices widely used in Italy to discriminate between the three clusters. The indices are: BMWP’ (British Monitoring Working Party, modified for Spain), ASPT (Average Score Per Taxon, modified for Spain), EBI (Extended Biotic Index) and IBE (Indice Biotico Esteso). BMWP’ and ASPT’ showed the best results. BMWP’ and ASPT’ scores — but not those of EBI and IBE — were sensitive to the different sampling methods utilised. We concluded that in this type of river stretch, BMWP’ and ASPT’ could be more useful than EBI and IBE although the relative efficiency of the chosen sampling method should be taken into account.

Temporal pattern of macroinvertebrate diversity and production in a new man made shallow lake

The construction of an aquatic system to recycle the wastewater coming from an experimental aquaculture plant provided the opportunity to follow the evolution of structural and functional properties of a community in a new eutrophic shallow lake. Specific aims of this study were to describe the temporal patterns of diversity and production of the macroinvertebrate assemblage in different habitats. The benthic assemblage was sampled monthly for 3 years starting 1 month after pond filling. Each month, replicate samples of invertebrates were collected with quantitative methods from 3 habitats: unvegetated bottom, submerged vegetation and emergent vegetation of the littoral zone. We collected a total of 48 macroinvertebrate taxa belonging to 38 families. The number of taxa increased rapidly during the first phase of colonization (93% of taxa were already recorded within 14 months from pond filling) and then slowly decreased through the next 2 years. Diversity pattern through time was not consistent among habitats, being higher in the unvegetated bottom during the first year and on the submerged vegetation and the littoral vegetation in subsequent years. Slopes of rank-abundance curves showed differences among years and habitats, even though all habitats showed a trend towards the increase of the relative dominance of few taxa (e.g. diminishing of slopes). Macroinvertebrate production changed with time and was different among habitats. The development of submerged and emergent macrophytes greatly increased not only the diversity, but also the production of the whole macroinvertebrate assemblage. %

Fluctuating asymmetry, size and mating success in males of Ischnura elegans (Vander Linden) (Odonata: Coenagrionidae)

Fluctuating asymmetry (FA) is thought to be an indicator of developmental stability and negatively related to male mating success in many animal taxa. We investigated the relationships between mating success of males, body size and FA for both wing length and number of setae on the legs in the damselfly Ischnura elegans. Males were classified as mated or unmated at the time of sampling. Fluctuating asymmetry, expressed as right-left differences, showed normal distributions without evidence of directional asymmetry or antisymmetry. Univariate analyses showed a significant negative correlation between size and mating success, and significant negative correlations between FA and mating success for both characters. On the other hand, with a multivariate analysis, new to studies on FA, the effect of body size was still significant but FA did not reach significance for either character. We conclude that the multivariate analysis should be used to assess the role of the different factors affecting mating success. Copyright 2000 The Association for the Study of Animal Behaviour.

Size structure of benthic invertebrate assemblages in a Mediterranean river

We examined the temporal, longitudinal, and among-substrate variation of the size structure of the invertebrate assemblage in a Mediterranenan river (Aniene River, central Italy). Sampling was conducted with quantitative methods on different substrates every 2 mo at 2 sites for 1 y and at 9 additional sites in spring 1997. Water-quality variables, periphyton standing crop, and physical characteristics of sites were also recorded. The Aniene River showed large longitudinal changes in overall physical features, periphyton biomass, and water quality that were reflected in dramatic changes of the taxonomic composition of the invertebrate assemblage. Insects were numerically dominant in the upper reach and codominant with gastropods in the middle reach, whereas oligochaetes, crustaceans, and chironomids were predominant in the lower and polluted reach. Despite these changes, the shape of the size structure of the invertebrate assemblage was similar among sites, dates, and substrates, with limited departures from the average size spectrum. Body mass alone accounted for the largest part of the variance of the abundance per size class (48%) whereas date, site, and substrate accounted for an additional 13%. These data support early observations of size spectrum invariance from North American streams and rivers, reinforcing the view that size-dependent processes may structure lotic benthic assemblages.

Fluctuating asymmetry, mating success, body size and heterozygosity in Coenagrion scitulum (Rambur) (Odonata: Coenagrionidae)

Abstract For decades fluctuating asymmetry (FA) has been considered a good descriptor of developmental stability. Correlations have been shown between FA and several fitness components, including mating success and heterozygosity level. However, some doubts have been expressed about the generalization of these results, perhaps because of bias towards positive results and a poor critical approach in the first phase of FA studies. Studies on Odonata are scarce and are concentrated on the Coenagrionidae family, with contrasting results in the relationships between FA and mating success, size and other fitness components. We investigated the relationships between FA expressed as right−left wing length (R−L), body size expressed as (R+L)/2, multilocus and single locus heterozygosity assessed by allozyme electrophoresis and short-term mating success (SMS) assessed from the status (mated or not) of the males at the moment of collection. We collected 260 males from a breeding population. The data were analysed by both univariate and multifactorial statistical methods. After excluding a correlation between FA and body size, we checked the presence of a true FA by using tests for normality, directional asymmetry, antisymmetry and difference from the interindividual variations. The results showed no correlation between FA (either signed or absolute) and heterozygosity, body size and SMS, while heterozygosity was clearly positively correlated with body size and with SMS. Our data suggest an effect of the presence of some particular alleles on SMS, instead of an effect of the multilocus heterozygosity, even if the presence of only three polymorphic loci weakens the conclusions. Finally, no correlation was found between body size and SMS.

Species distribution and habitat features in lentic Odonata

Abstract The relationships between species assemblages and pond characteristics were investigated in a well preserved Mediterranean coastal woodland. Data on adult abundance were collected fortnightly. Pond area and depth, shade, riparian vegetation, presence of four classes of aquatic plants, presence of fish and both the distances from pond to pond and from pond to sea were considered as pond features. Results showed the presence of 23 Odonata species on 23 ponds. A Mantel test showed that the matrices of pond to pond topographic distances and that of pond to pond faunistic similarity were independent, which supports the hypothesis that the adult Odonata actively choose their breeding site. A stepwise multiple regression showed that only pond size, minimum water level and riparian vegetation had significant effects (all positive) on the total number of Odonata species in each pond. On the other hand, a canonical correspondence analysis showed that the composition of Odonata species assemblages was sensitive to almost all variables. From the point of view of Odonata conservation, both the moderate effect of Gambusia hol‐brooki and the positive effect of the riparian vegetation on the number of Odonata species appear particularly interesting for restoring or creating Odonata habitats.

Cave crickets and cave weta (Orthoptera, Rhaphidophoridae) from the southern end of the World: a molecular phylogeny test of biogeographical hypotheses

Abstract In this study we reconstructed the molecular phylogeny and attempted to infer historical biogeography of a sample of cricket species, most of them cave-dwelling, belonging to the subfamily Macropathinae (Orthoptera, Rhaphidophoridae) which shows a clear Gondwanan distribution. We sequenced fragments of 4 genes (12S rRNA, 16S rRNA, 18S rRNA and 28S rRNA), for a total of 1993 bp. We present here preliminary data based on a total of 17 species, 11 belonging to Macropathinae and representative of the main regions of Gondawanaland, 7 to Aemodogryllinae and Rhaphidophorinae from India, Bhutan, China, Philippines and the Sulawesi Islands. The use of relaxed molecular clocks by means of Bayesian analysis allowed us to estimate the timing of the main cladogenetic events, using calibration of a molecular clock; the clock is based on the plate disjunction of Africa from South America, Australia from Zealandia (New Zealand), or Australia from Antarctica. The latter was considered at two different datings on the basis of two alternative palaeogeographic hypotheses. Node dating using separation of Africa or a model of earlier separation of Australia from Antarctica, suggests that the main cladogenetic events in the Macropathinae phylogeny could be explained by vicariance hypotheses, related to the Gondwana fragmentation. However, two other equally valid calibrations suggest that lineage formation is not consistent with vicariant processes and requires either some long-distance dispersal, or an inconceivable age of origin of this family of insects, enabling the prior existence of all lineages in Gondwanaland with subsequent regional extinction.

The benthic community structure in mountain ponds affected by livestock watering in nature reserves of Central Italy.

In pond ecosystems nurrient enrichment can cause a shift from a clear water state dominated by aquatic macrophytes to a turbid water state dominated by phytoplankton (SCHEFFER et al. 1993). This shift is the result of complex interactions, occurring in the pelagic and the benrhic habitats, between the biota and physical, chemical and biological variables such as water depth, extension of macrophyte coverage and resuspension of sediments (SCHEFFER et al. 1993). The presence of submerged macrophytes has a strong influence on benthic invertebrates (SCHEFFER 1998) so that a shift from the clear to the turbid state may result in an abrupt change of the macrobenthic community structure and in a loss of a considerable portion of invertebrate diversity. In fact, in the clear state, large sized grazers, such as snails and ephemeropterans, consume the periphyron that can grow on floating and submerged plants and dominate the community. On the other hand, in the turbid state, filtering and gathering collectors, such as oligochaetes and chironomids, can become dominant, feeding on the organic matter which falls down from the productive pelagic habitat. Moreover, a larger number o f invertebrate predators ( e.g. zigopterans, some dipterans and coleopterans) are associated with dense vegetation cover, while few taxa (e.g. anisopterans and other dipterans) are associated with macrophyte free habitats. Since macroinvertebrates are a major food source for many fish species, the change in macroinvertebrate community composition has important consequences for the abundance and the size strucrure of many fish species (DIEHL & KoRNIJOW 1997). Thus, the effects of fertilization may cascade down from the pelagic to the benthic habitat and back again, the benrhic community playing a major role in this process. The mountain area of central Italy (Appennino Centrale), mainly formed by calcareous rocks, is characterized by a scarcity of surface water over l ,000 m a. s.!. In this area the few natural an d artificial ponds, often located in natural parks, represent unique and valuable freshwater ecosystems. However, the clear state (an d so a great portion o f invertebrate diversity) of many of these ponds is threatened because of the fertilization coming from the massive excretion and physical disrurbance of cattle that feed in the area and drink the water during the summer months. As a first step toward a larger research programme whose final objective is to evaluate the integration of human activities with the conservation needs of the area, we aimed to clarifY the relationship berween the nurrient enrichment and the macrobenrhic community structure and diversity of several ponds.

A new Polygordius (Annelida: Polychaeta) from Terra Nova Bay, Ross Sea, Antarctica

Abstract Polygordius antarcticus sp. nov. is described from benthic material collected at depths ranging between 31 and 61 m in Terra Nova Bay, Ross Sea, during the 1987–1988 and 1988–1989 expeditions of the Italian National Research Program in Antarctica. This is the first named species of the genus from Antarctic waters. Although no fully mature specimens were available, the new species appears unique in combining the following features: a regular pygidium, inflated and with a single ring of round adhesive pads, a conical prostomium with short antennae (only half as long as the prostomium) and shallow head fold, and a well-developed circulatory apparatus, with circumoesophageal commissures entering the prostomium and long intersegmental commissures insinuating into the ventrolateral compartments of the trunk. These and other significant features were investigated by light and scanning electron microscopy. In the construction of the head and the scheme of the blood system, the new species resembles Polygordius triestinus Woltereck, described by Hempelmann in 1906, an aberrant species inhabiting muddy, anoxic sediments in the Adriatic Sea, but it differs significantly from it in the shape of the mouth (in P. triestinus the upper lip is hypertrophied and strongly protruding) and the pygidium (in P. triestinus this region is stump-like and non-adhesive). The pygidium of P. antarcticus sp. nov. is encircled by 28–30 small adhesive pads, each with 15–20 glandular openings. Preterminal cirri are lacking, as are perianal appendages. The anus is surrounded by six to seven lobes of which the midventral is largest and longest. A world distribution map of the genus is provided.

Life history and species composition of the damselfly assemblage along the urban tract of a river in central Italy

The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution were different between the sampling sites showing that the life history of both species examined were influenced by a degradation of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites.