Unravelling some Kinki earthworms (Annelida: Oligochaeta: Megadrili: Megascolecidae) - Part II

Robert J. Blakemore

Opusc. Zool. Budapest (2010) 41(2), 191–206

Abstract. 

Metaphire tanbode sp. nov. is found in rice paddy in Kinki plain at Lake Biwa and Amynthas yamade sp. nov. is from Hira range to the West. M. tanbode belongs to the M. hilgendorfi / A. tokioensis species-complex, while montane A. yamade is comparable to both Amynthas aeruginosus-group and Duplodicodrilus schmardae-group. Genetic barcoding (mtDNA COI) via types is attempted. Taxonomic ‘housekeeping’ requires replacement of invalid homonyms: e.g. Pheretima montana Ishizuka, 1999 (non type-species P. montana Kinberg, 1867) is renamed Amynthas nonmontanus; others are A. nonsilvestris, A. noninvisus, A. nonmonticolus and A. nonsetosus, noms. et combs. novae. Thus Pheretima Kinberg, 1867 s. stricto remains unrecorded from Japan while prior Amynthas Kinberg, 1867, and its derivative Metaphire Sims & Easton, 1972, are abundant and diverse. Family and generic level definition and placement of Oriental pheretimoids are restated for the benefit of current workers and for novice field-ecologists. Surveys of below-ground biodiversity of rice paddy in Lake Biwa is compared to more natural habitats around Lake Pedder in Western Tasmanian Wilderness Area, and co-incidentally, both have 21 recorded earthworm species. Thus claims from various countries of less than six species per location are contraindicated by thorough eco-taxonomic methods yielding more representative results.

Impact of above- and below-ground invertebrates on temporal and spatial stability of grassland of different diversity

Nico Eisenhauer, Alexandru Milcu, Eric Allan, Norma Nitschke, Christoph Scherber, Vicky Temperton, Alexandra Weigelt, Wolfgang W. Weisser and Stefan Scheu

Journal of Ecology (2011) 99, 572–582

Summary

1. Recent theoretical studies suggest that the stability of ecosystem processes is not governed by diversity per se, but by multitrophic interactions in complex communities. However, experimental evidence supporting this assumption is scarce.

2. We investigated the impact of plant diversity and the presence of above- and below-ground invertebrates on the stability of plant community productivity in space and time, as well as the interrelationship between both stability measures in experimental grassland communities.

3. We sampled above-ground plant biomass on subplots with manipulated above- and belowground invertebrate densities of a grassland biodiversity experiment (Jena Experiment) 1, 4 and 6 years after the establishment of the treatments to investigate temporal stability. Moreover, we harvested spatial replicates at the last sampling date to explore spatial stability.

4. The coefficient of variation of spatial and temporal replicates served as a proxy for ecosystem stability. Both spatial and temporal stability increased to a similar extent with plant diversity.Moreover, there was a positive correlation between spatial and temporal stability, and elevated plant density might be a crucial factor governing the stability of diverse plant communities.

5. Above-ground insects generally increased temporal stability, whereas impacts of both earthworms and above-ground insects depended on plant species richness and the presence of grasses. These results suggest that inconsistent results of previous studies on the diversity–stability relationship have in part been due to neglecting higher trophic-level interactions governing ecosystem stability.

6. Changes in plant species diversity in one trophic level are thus unlikely to mirror changes in multitrophic interrelationships. Our results suggest that both above- and below-ground invertebrates decouple the relationship between spatial and temporal stability of plant community productivity by differently affecting the homogenizing mechanisms of plants in diverse plant communities.

7. Synthesis. Species extinctions and accompanying changes in multitrophic interactions are likely to result not only in alterations in the magnitude of ecosystem functions but also in its variability complicating the assessment and prediction of consequences of current biodiversity loss.

Earthworm Invasion as the Driving Force Behind Plant Invasion and Community Change in Northeastern North American Forests

VICTORIA A. NUZZO, JOHN C. MAERZ, AND BERND BLOSSEY

Conservation Biology (2009) 23(4) 966–974

Abstract

Identification of factors that drive changes in plant community structure and contribute to decline and endangerment of native plant species is essential to the development of appropriate management strategies. Introduced species are assumed to be driving causes of shifts in native plant communities, but unequivocal evidence supporting this view is frequently lacking. We measured native vegetation, non-native earthworm biomass, and leaf-litter volume in 15 forests in the presence and absence of 3 non-native plant species (Microstegium vimineum, Alliaria petiolata, Berberis thunbergii) to assess the general impact of non-native plant and earthworm invasions on native plant communities in northeastern United States. Non-native plant cover was positively correlated with total native plant cover and non-native earthworm biomass. Earthworm biomass was negatively associated with cover of native woody and most herbaceous plants and with litter volume. Graminoid cover was positively associated with non-native earthworm biomass and non-native plant cover. These earthworm-associated responses were detected at all sites despite differences in earthworm species and abundance, composition of the native plant community, identity of invasive plant species, and geographic region. These patterns suggest earthworm invasion, rather than non-native plant invasion, is the driving force behind changes in forest plant communities in northeastern North America, including declines n native plant species, and earthworm invasions appear to facilitate plant invasions in these forests. Thus, a focus on management of invasive plant species may be insufficient to protect northeastern forest understory species.

Dietary flexibility aids Asian earthworm invasion in North American forests

WEIXIN ZHANG, PAUL F. HENDRIX, BRUCE A. SNYDER, MARIROSA MOLINA, JIANXIONG LI, XINGQUAN RAO, EVAN SIEMANN, AND SHENGLEI FU

Ecology (2010) 91(7) 2070–2079

Abstract

On a local scale, invasiveness of introduced species and invasibility of habitats together determine invasion success. A key issue in invasion ecology has been how to quantify the contribution of species invasiveness and habitat invasibility separately. Conventional approaches, such as comparing the differences in traits and/or impacts of species between native and/or invaded ranges, do not determine the extent to which the performance of invaders is due to either the effects of species traits or habitat characteristics. Here we explore

the interaction between two of the most widespread earthworm invaders in the world (Asian Amynthas agrestis and European Lumbricus rubellus) and study the effects of species invasiveness and habitat invasibility separately through an alternative approach of ‘‘third habitat’’ in Tennessee, USA. We propose that feeding behaviors of earthworms will be critical to invasion success because trophic ecology of invasive animals plays a key role in the invasion process. We found that (1) the biomass and isotopic abundances (d13C and d15N) of A. agrestis were not impacted by either direct effects of L. rubellus competition or indirect effects of L. rubellus-preconditioned habitat; (2) A. agrestis disrupted the relationship between L. rubellus and soil microorganisms and consequently hindered litter consumption by L. rubellus; and (3) compared to L. rubellus, A. agrestis shifted its diet more readily to consume more litter, more soil gram-positive (Gþ) bacteria (which may be important for litter digestion), and more nonmicrobial soil fauna when soil microorganisms were depleted. In conclusion, A. agrestis showed strong invasiveness through its dietary flexibility through diet shifting and superior feeding behavior and its indirectly negative effect of habitat invasibility on L. rubellus via changes in the soil microorganism community. In such context, our results expand on the resource fluctuation hypothesis and support the superior competitor hypothesis. This work presents additional approaches in invasion ecology, provides some new dimensions for further research, and contributes to a greater understanding of the importance of interactions between multiple invading species.

Re-integrating earthworm juveniles into soil biodiversity studies: species identification throughDNAbarcoding

B. RICHARD, T. DECAE¨NS, R. ROUGERIE, S. W. JAMES, D. PORCO and P. D. N. HEBERT

Molecular Ecology Resources (2010) 10, 606–614


Abstract

Species identification of earthworms is usually achieved by careful observation of morphological features, often sexual characters only present in adult specimens. Consequently, juveniles or cocoons are often impossible to identify, creating a possible bias in studies that aim to document species richness and abundance.DNA barcoding, the use of a short standardized DNA fragment for species identification, is a promising approach for species discrimination. When a reference library is available, DNA-based identification is possible for all life stages. In this study, we show that DNA barcoding is an unrivaled tool for high volume identification of juvenile earthworms. To illustrate this advance,we generated DNA barcodes for specimens of Lumbricus collected from three temperate grasslands in western France. The analysis of genetic distances between individuals shows that juvenile sequences unequivocally match DNA barcode clusters of previously identified adult specimens, demonstrating the potential of DNA barcoding to provide exhaustive specimen identification for soil ecological research.

Cryptic speciation of hormogastrid earthworms revealed by mitochondrial and nuclear data

Marta Novo, Ana Almodóvar, Rosa Fernández, Dolores Trigo, Darío J. Díaz Cosín

Molecular Phylogenetics and Evolution (2010) 56, 507–512


Abstract

Species delimitation of earthworms has been difficult to determine with certainty due to their structural simplicity. We sequenced fragments of COI, 16S, t-RNAs and 28S for 202 Hormogastridae individuals from the central Iberian Peninsula and three outgroup taxa. A morphological constancy was found but a high genetic diversity suggests the presence of five cryptic allopatric species. Results showed a pattern of isolation by distance and a positive but weak correlation between some soil properties (coarse sand and total loam content) and genetic distances, which indicates that these populations may have been shaped genetically but not morphologically, by the environment.

High mitochondrial DNA sequence diversity in the parthenogenetic earthworm Dendrobaena octaedra

KE Knott and J Haimi

Heredity (2010) 105, 341–347

Abstract

Apomictic parthenogens are clonal organisms with limited genetic opportunity for increasing diversity beyond mutation. However, such species can be successful and have been shown to harbor more genetic diversity than might be expected. Here we surveyed diversity of the cytochrome oxidase subunit I gene from the mitochondrial genome of the earthworm Dendrobaena octaedra, an apomictic parthenogen. Diversity estimates made previously from allozyme markers for this species were high, but could have been affected by a detection bias, namely variable expression of alleles in the polyploid genome. We found similarly high mtDNA diversity over three localities in Finland, each represented by two sites; either with or without anthropogenic soil metal contamination. A single haplotype was most common over all sites, and over two thirds of all haplotypes sampled were similar to it in sequence (only varying by 1–3 substitutions). However, more divergent rare haplotypes were also found in one locality, Imatra, in southeast Finland close to the Karelian Isthmus. Metal contamination in the soil did not have a significant effect on genetic diversity, although metal exposure is known to be detrimental to the worms. There was no evidence for cryptic species within D. octaedra and phylogenetic analyses showed some structure of lineages that may have diverged in historical glacial refugia. Other mechanisms, such as rare genetic exchange with closely related species or high mutation and dispersal rates may explain high genetic diversity in D. octaedra. 

DNA Barcoding Reveals Cryptic Diversity in Lumbricus terrestris L., 1758 (Clitellata): Resurrection of L. herculeus (Savigny, 1826)

Samuel W. James, David Porco, Thibaud Decaens, Benoit Richard, Rodolphe Rougerie, Christer Erseus

PLoS ONE (2010) 5(12), e15629. doi:10.1371/journal.pone.0015629

Abstract

The widely studied and invasive earthworm, Lumbricus terrestris L., 1758 has been the subject of nomenclatural debate for many years. However these disputes were not based on suspicions of heterogeneity, but rather on the descriptions and nomenclatural acts associated with the species name. Large numbers of DNA barcode sequences of the cytochrome oxidase I obtained for nominal L. terrestris and six congeneric species reveal that there are two distinct lineages within nominal L. terrestris. One of those lineages contains the Swedish population from which the name-bearing specimen of L. terrestris was obtained. The other contains the population from which the syntype series of Enterion herculeum Savigny, 1826 was collected. In both cases modern and old representatives yielded barcode sequences allowing us to clearly establish that these are two distinct species, as different from one another as any other pair of congeners in our data set. The two are morphologically indistinguishable, except by overlapping size-related characters. We have designated a new neotype for L. terrestris. The newly designated neotype and a syntype of L. herculeus yielded DNA adequate for sequencing part of the cytochrome oxidase I gene (COI). The sequence data make possible the objective determination of the identities of earthworms morphologically identical to L. terrestris and L. herculeus, regardless of body size and segment number. Past work on nominal L. terrestris could have been on either or both species, although L. herculeus has yet to be found outside of Europe.