Pietro Paolo Fanciulli

Deep phylogeographic divisions and long‐term persistence of forest invertebrates (Hexapoda: Collembola) in the North‐Western Mediterranean basin

The North‐Western Mediterranean basin is well known for its high number of relictual endemic taxa, and has been indicated as one of the world’s major biodiversity hotspots at the species level. A possible contributing factor may be long‐term persistence of populations and their prolonged stability. This study was designed to investigate the phylogeographic structure of three common species of the genus Lepidocyrtus (Hexapoda: Collembola), soil‐dwelling arthropods characterized by limited dispersal capabilities and generally associated with forest habitats. We observed a remarkable geographic structure, with numerous deeply divergent genetic lineages occupying islands as well as mainland sites with no apparent gene flow among most sites, even across distances of only tens of kilometres. The reconstructed time frame for the evolution of these lineages suggests divergence between 5 and 15 Ma. This indicates a remarkably ancient origin and long‐term persistence of individual lineages over a fine geographic scale despite the occurrence of abrupt sea level and climatic fluctuations in the area. This further suggests that currently recognized morphological species might be a serious underestimation of the true springtail biodiversity within this region.

Phylogeny, phylogeography, phylobetadiversity and the molecular analysis of biological communities

There has been much recent interest and progress in the characterization of community structure and community assembly processes through the application of phylogenetic methods. To date most focus has been on groups of taxa for which some relevant detail of their ecology is known, for which community composition is reasonably easily quantified and where the temporal scale is such that speciation is not likely to feature. Here, we explore how we might apply a molecular genetic approach to investigate community structure and assembly at broad taxonomic and geographical scales, where we have little knowledge of species ecology, where community composition is not easily quantified, and where speciation is likely to be of some importance. We explore these ideas using the class Collembola as a focal group. Gathering molecular evidence for cryptic diversity suggests that the ubiquity of many species of Collembola across the landscape may belie greater community complexity than would otherwise be assumed. However, this morphologically cryptic species-level diversity poses a challenge for attempts to characterize diversity both within and among local species assemblages. Recent developments in high throughput parallel sequencing technology, combined with mtDNA barcoding, provide an advance that can bring together the fields of phylogenetic and phylogeographic analysis to bear on this problem. Such an approach could be standardized for analyses at any geographical scale for a range of taxonomic groups to quantify the formation and composition of species assemblages.

High levels of genetic variability and population differentiation in Gressittacantha terranova (Collembola, Hexapoda) from Victoria Land, Antarctica

Allozyme electrophoresis was used to assess genetic variability and differentiation in 22 populations of Gressittacantha terranova Wise (Hexapoda, Collembola) from a coastal area of Victoria Land between the Mariner Glacier and the Nansen Ice Sheet. Allelic frequencies were determined at five enzyme loci: Phi, Pgm, Hk, Mpi and Mdh. Levels of variability, estimated as rates of heterozygosity, were higher than those calculated for the same loci in taxonomically related and non-related species of non-Antarctic Collembola. Thus, in spite of the ecological simplicity of Antarctic terrestrial ecosystems, G. terranova is characterized by high levels of genetic variability, and the 22 populations could be divided into three geogaphic groups, separated by the Aviator and Campbell glaciers. Genetic differentaton reflects the geographic arrangement of the populations, suggesting that the glaciers are effective barriers to gene flow, and that the patchy distribution of collembolan species in Antarctica has the potential to induce, in the long term, microspeciation processes. Interestingly, detectable genetic differentiation was observed between six populations collected at Edmonson Point, even though these are very close to each other, indicating the impact of geographic isolation even within short distances. The only exception to the congruence between genetic and geographic structuring was provided by the population of Apostrophe Island, for which a recent introduction with individuals coming from southern populations is suggested.

Allozyme variation in reference and metal-exposed natural populations of Orchesella cincta (insecta: Collembola)

Environmental pollution may affect genetic variation in populations inhabiting polluted sites. In this study, allozyme variation was studied in natural populations of the soil-dwelling insect Orchesella cincta. The populations originated from eight sites with different histories of metal contamination and natural enrichment in The Netherlands, Belgium and F.R.G. Slight but significant divergence was observed for four polymorphic loci; 18 lociwere monomorphic at all sites. The highest mean values for heterozygosity (H), degree of polymorphism (P) and mean number of alleles per locus (A) were 0.090, 0.182 and 1.36, respectively. Geographic distance was not correlated to genetic divergence. Comparison of allozyme data from investigated populations and from a reference population in Italy showed a remarkable genetic homogeneity in this species, the highest value for Neis genetic distance (D) being 0.035. Among NW European populations, a correlation between metal tolerance characteristics and allozyme frequencies was observed for glutamate-oxaloacetate transaminase (Ec. 2.6.1.1).

The use of genetic markers for the diagnosis of sibling species in the genus Isotomurus (Insecta, Collembola)

Abstract Two independent genetic markers (allozymes and mitochondrial DNA sequences) were used to demonstrate that Isotomurus palustris palustris and Isotomurus palustris maculatus (Collembola, Isotomidae), interpreted either as varieties or subspecies by the various authors, are, actually, well differentiated species. Specimens were collected sympatrically in five different sampling sites in Italy and southern France, and, in all of them, the two forms were fixed for alternative alleles at some enzyme loci. The absence of hybrids demonstrates that the two species, discriminated morphologically by body pigmentation, do not cross. The rate of sequence divergence of the mitochondrial COII gene confirms a significant degree of differentiation.

Collembola, the biological species concept and the underestimation of global species richness

Despite its ancient origin, global distribution and abundance in nearly all habitats, the class Collembola is comprised of only 8000 described species and is estimated to number no more than 50 000. Many morphologically defined species have broad geographical ranges that span continents, and recent molecular work has revealed high genetic diversity within species. However, the evolutionary significance of this genetic diversity is unknown. In this study, we sample five morphological species of the globally distributed genus Lepidocyrtus from 14 Panamanian sampling sites to characterize genetic diversity and test morphospecies against the biological species concept. Mitochondrial and nuclear DNA sequence data were analysed and a total of 58 molecular lineages revealed. Deep lineage diversification was recovered, with 30 molecular lineages estimated to have established more than 10 million years ago, and the origin almost all contemporary lineages preceding the onset of the Pleistocene (~2 Mya). Thirty‐four lineages were sampled in sympatry revealing unambiguous cosegregation of mitochondrial and nuclear DNA sequence variation, consistent with biological species. Species richness within the class Collembola and the geographical structure of this diversity are substantially misrepresented components of terrestrial animal biodiversity. We speculate that global species richness of Collembola could be at least an order of magnitude greater than a previous estimate of 50 000 species.

Chromosome elimination and sex determination in springtails (Insecta, Collembola).

A post-zygotic mechanism of sex determination is described in the two symphypleonans Dicyrtomina ornata (Nicolet) and Ptenothrix italica Dallai. The process consists of the loss of two sex chromosomes from the male embryo. At the end of the first meiotic division of spermatogenesis, a second chromosome elimination occurs, allowing half the secondary spermatocytes, later transformed into spermatids, to receive a complete haploid set of chromosomes. The secondary spermatocytes, which receive an incomplete set of chromosomes, degenerate. Males of the two collembolan species, therefore, produce a reduced number (50%) of spermatozoa. Females of D. ornata have 2n = 12 and males 2n = 10 chromosomes; females of P. italica have 2n = 14 and males 2n = 12 chromosomes. In both species, oogenesis proceeds normally and chromosomes pair and form chiasmata in meiotic prophase. The adaptive significance of this post-zygotic mechanism of sex determination is discussed. The mechanism seems to be a characteristic feature of the suborder Symphypleona. The neanurid Arthropleona Anurida maritima (Guérin), which was studied for comparative analysis, has 2n = 8 chromosomes and normal spermatogenesis producing haploid nuclei with four chromosomes. J. Exp. Zool. (Mol. Dev. Evol.) 285:215-225, 1999.

Ultrastructure of the male accessory glands ofAllacma fusca(Insecta, Collembola)☆

The accessory glands ofAllacma fusca(L.) (Insecta, Collembola, Sminthuridae) consist of a series of secretory units that are arranged in parallel and open into the ejaculatory duct. Each unit is composed of microvillate cells stacked around a common cavity. Basal cells are involved in ion-control of fluids from the hemocoel to the cavity. The intermediate and apical cells, which have a laminar appearance and contain many microtubules, are involved in the structural integrity of the unit. Supporting cells ensheath the most apical cells. Large openings in the cuticle allow the gland secretion to flow into the ejaculatory duct lumen. These openings are protected by a porous cuticle different from that lining the epithelium of the ejaculatory duct. Conspicuous muscle fibers run along the lateroventral side of the ejaculatory duct beneath the insertion of the accessory glands. The fine structure of the accessory glands indicates that they are type I ectodermic glands as defined by Noirot & Quennedey (1974). Their function could be to control the fluidity of the material for spermatophore formation and to ensure the proper physiological conditions for spermatozoa stored in the ejaculatory duct lumen.

Comparative analysis of two edaphic zoocoenoses (Acari Oribatida; Hexapoda Collembola) in the area of Orio al Serio Airport (Bergamo, northern Italy)

Species richness, abundance and diversity of oribatid mites and springtails in soil and litter were investigated at four sites in the area of Orio al Serio Airport (Bergamo, Italy). A total of 60 oribatid mite and 35 springtail species were collected from the sites. The general low diversity and evenness along with high dominance may be related to the sensitivity of these edaphic zoocoenoses to soil impoverishment which has been occurring in this part of the Italian pre-Alps for many years. Quantitative and qualitative differences were found among the investigated areas. Results show that less frequently disturbed soils are capable of restoring oribatid and springtail populations, leading to greater equilibrium. Results show that less frequently disturbed soils allow the restoration of more equilibrated oribatid and springtail populations. Species were divided into 8 autoecological and 11 chorological categories. Correspondence Analysis arranged these categories among the sites, confirming the above-mentioned trend.

The ultrastructure of the spermathecae in the Collembola Symphypleona (Hexapoda)

The fine structure of the paired spermathecae of two Symphypleona Collembola, Sminthurus viridis and Allacma fusca, was studied. The spermathecal epithelium is rich in pigment granules, while secretory organelles are scarce, consisting of a few mitochondria and microtubules, scattered cisterns of endoplasmic reticulum and Golgi systems. Small isolated secretory granules are visible in the apical cell region, where irregular microvilli are present. Beneath the epithelium, large cells rich in endoplasmic reticulum and Golgi systems are present; they are separated from the epithelial cells by a thin basal lamina. The epithelium is lined by a thin cuticle, which forms thin extensions at the beginning of the spermathecal duct. At this level, muscle fibers are visible. The spermathecal lumen is filled with many spermatozoa. At molting, the spermathecal epithelial cells detach from the cuticle and a large electron‐transparent space is evident between the cytoplasm and the cuticle. The cytoplasm has few pigment granules and the spermathecal lumen contains degenerating spermatozoa. After 3 days, the spermathecal epithelium regains its usual appearance and the spermathecal lumen is empty. The two species of Collembola Symphypleona do not have accessory glands. Compared with the Arthropleona Orchesella villosa, which has a single spermatheca and two accessory glands (Dallai et al. 2008 J Morphol 269:464–478), a great difference has occurred in the organization of the female genital system of these species. The results are discussed in light of the implications for reproductive behavior and egg protection in Symphypleona. J. Morphol., 2008.