Levels of endemism are not necessarily biased by the co-presence of species with different range sizes: a case study of Vilenkin and Chikatunov's models

Aim  To illustrate problems in the methods proposed by B. Vilenkin and V. Chikatunov to study levels of endemism and species–area relationships.
Location  The study used data on the distribution of tenebrionid beetles (Coleoptera, Tenebrionidae) on the Aegean Islands (Greece).
Methods  A total of 32 islands and 170 taxa (species and subspecies) were included in this study. Levels of endemism were evaluated both as the proportion of endemic taxa, and according to the methods proposed by Vilenkin and Chikatunov, which are based on the number of non-endemic taxa and various relationships with area. A model of the species–area relationship proposed by these authors was also analysed.
Results  The number of endemic taxa was positively correlated with the number of taxa with different distribution types, but this positive correlation did not influence the estimation of the level of endemism. In fact, the commonly used estimate of endemicity as a percentage was strongly correlated with the endemism values calculated according to the method of Vilenkin and Chikatunov. The usual power function fitted the species–area relationship as well as the most complicated method of Vilenkin and Chikatunov.
Main conclusions  As hypothesized by Vilenkin and Chikatunov, the number of endemic taxa was influenced both by the number of taxa of other biogeographical ranks, and by an island's area. However, explanations for the positive relationship between the number of endemic taxa and taxa of different biogeographical ranks are equivocal. Importantly, this relationship did not necessarily influence the level of endemism, which could be expressed adequately by percentages. The method proposed by Vilenkin and Chikatunov to estimate the species–area relationship cannot be clearly justified on theoretical grounds and is of questionable practical utility.     

A mixture of begomoviruses in leaf curl-affected tobacco in Karnataka, South India

Tobacco leaf curl is widespread in several states in India including Andhra Pradesh, Gujarat, Karnataka, Bihar and West Bengal. Tobacco leaf curl virus (TbLCV) isolates collected from five different parts of India induced four distinct symptom phenotypes (group I, II, III & IV) on tobacco cultivars Samsun and Anand 119 (Valand & Muniyappa, 1992). PCR was performed on DNA extracted from group I and IV leaf curl‐affected tobacco from Karnataka, India using degenerate begomovirus‐specific primers. Subsequent cloning and sequencing of PCR products revealed preliminary evidence for the presence of at least three begomoviruses in the affected material following alignment of a 333 bp region of the coat protein gene (CP). The complete CP and common region (CR) of two putative begomoviruses, Tobacco leaf curl virus‐Karnataka1 (TbLCV‐Kar1) and Tobacco leaf curl virus‐Karnataka2 (TbLCV‐Kar2), were sequenced using PCR clones obtained with designed sequence‐specific primers. Phylogenetic analysis of the CP and CR of TbLCV‐Kar1 and TbLCV‐Kar2 placed them in the Asian Old World begomovirus cluster. The two viruses differed from each other significantly in both the CP gene and the CR (< 90% nucleotide sequence identity). This difference, in conjunction with distinct iterative sequences strongly suggests that these begomoviruses are distinct from one another. Group I and IV tobacco were also found to harbour a possible third begomovirus following the 333 bp CP alignment. Comparison of TbLCV‐Kar1 and TbLCV‐Kar2 with other geminiviruses, showed that both sequences shared high nucleotide sequence identity (> 90%) with other begomoviruses in either the CP or CR, thereby suggesting these viruses to be possible strains of other reported begomoviruses. Combined comparison of the CP and CR sequences however, suggests that the two viruses are not strains of other reported begomoviruses, but may be distinct begomoviruses that could have arisen through recombination events during mixed infections. Phylogenetic comparison demonstrated no significant homology between the Indian tobacco begomoviruses and a tobacco‐infecting begomovirus from Zimbabwe, again showing that as with other geminiviruses, there is a geographic basis for phylogenetic relationships rather than an affiliation with tobacco as a host.     

Re‐approaching the small island effect

Aim To propose a new approach to the small island effect (SIE) and a simple mathematical procedure for the estimation of its upper limit. The main feature of the SIE is that below an upper size threshold an increase of species number with increase of area in small islands is not observed. Location Species richness patterns from different taxa and insular systems are analysed. Methods Sixteen different data sets from 12 studies are analysed. Path analysis was used for the estimation of the upper limit of the SIE. We studied each data set in order to detect whether there was a certain island size under which the direct effects of area were eliminated. This detection was carried out through the sequential exclusion of islands from the largest to the smallest. For the cases where an SIE was detected, a log‐log plot of species number against area is presented. The relationships between habitat diversity, species number and area are studied within the limits of the SIE. In previous studies only area was used for the detection of the SIE, whereas we also encompass habitat diversity, a parameter with well documented influence on species richness, especially at small scales. Results An SIE was detected in six out of the 16 studied cases. The upper limit of the SIE varies, depending on the characteristics of the taxon and the archipelago under study. In general, the values of the upper limit of the SIE calculated according to the approach undertaken in our study differ from the values calculated in previous studies. Main conclusions Although the classical species–area models have been used to estimate the upper limit of the SIE, we propose that the detection of this phenomenon should be undertaken independently from the species–area relationship, so that the net effects of area are calculated excluding the surrogate action of area on other variables, such as environmental heterogeneity. The SIE appears when and where area ceases to influence species richness directly. There are two distinct SIE patterns: (1) the classical SIE where both the direct and indirect effects of area are eliminated and (2) the cryptic SIE where area affects species richness indirectly. Our approach offers the opportunity of studying the different factors influencing biodiversity on small scales more accurately. The SIE cannot be considered a general pattern with fixed behaviour that can be described by the same model for different island groups and taxa. The SIE should be recognized as a genuine but idiosyncratic phenomenon.     

Gradual evolutionary transformations of ontogeny in an Ordovician ostracod lineage

Carapace morphology was studied biometrically for each instar in a series of populations of Mojczella Olempska 1988 from the Ordovician strata exposed in Mójcza, Holy Cross Mountains, Poland. Phosphatic coatings of ostracod valves occur there in abundance from the top of the Arenig to the Late Caradoc. The lineage shows smooth acceleration in ontogenetic expression of the junction of crests C1 and C3, which originally were separated throughout the ontogeny, while in the latest populations the separation was preserved only in the earliest moult stage. Moreover, the velar structure, being originally developed as a wide, slightly convex, flange-like dolon in heteromorphs, became transformed into a convex dolon.     

Growth of pikeperch in relation to lake characteristics: total phosphorus, water colour, lake area and depth

The growth of pikeperch Sander lucioperca was studied in 41 lakes in central Finland. The backcalculated average total length of 3 year‐old pikeperch was used as an indicator of growth. The growth correlated positively with total phosphorus and water colour and negatively with lake area and depth. The reason for differences in growth may be differences in the amount of suitable food, foraging success or temperature dynamics in different lakes.     

Tuber induction and initiation during production and early field growth of transplants from in vitro-derived potato plants

In transplants from in vitro‐derived plantlets from very early potato (Solanum tuberosum) cultivars, a lower degree of tuber induction at the time of field planting is thought to increase tuber production. Leaf‐bud cuttings were used to assess the progress to tuber induction in in vitro‐derived potato plantlets during the transplant production phase and after subsequent transplanting into the field. Induction and initiation of tubers on the same plants were assessed to study the effects of the duration of transplant production and conditions during transplant production for cv. Gloria (very early) and cv. Bintje (mid‐early). In vitro‐produced plantlets were not induced by the time of planting but rapidly progressed to the induced state thereafter. The progress in induction with time and the change in percentage of plants showing tubers fitted typical sigmoid curves. Plantlets achieved 50% induction ca 15 days after planting into in vivo conditions, and 50% tuber initiation usually occurred 10 days later. Shorter transplant production periods reduced the degree of induction of the transplants at field planting. Transplant production for more than 2 weeks was required to allow conditions during that period to affect induction or initiation. Long‐term non‐inducing conditions delayed the progress to tuber induction in cv. Gloria and delayed tuber initiation in both cultivars. Cv. Gloria showed no faster progress to induction than cv. Bintje but initiated tubers earlier. The results suggest that the relation between progress to induction and tuber initiation is cultivar dependent and that leaf‐bud cuttings can be used successfully in very young in vitro‐derived plants for assessing the progress to tuber induction.     

Species status and population structure of the Australian Eucalyptus pest Paropsis atomaria Olivier (Coleoptera: Chrysomelidae)

1 Paropsis atomaria Olivier represents an emergent pest of Eucalyptus plantations in Queensland and New South Wales, Australia. Most prior studies on the biology and control of P. atomaria have centred on populations from Canberra in the Australian Capital Territory, but the biological relationship between beetles from Canberra and those from up to 1500 km further north are unknown. 2 DNA markers were used to determine whether P. atomaria from Canberra are the same biological species as those from Eucalyptus forestry plantations in northern New South Wales and Queensland, where the beetle has become an important pest. Using the mitochondrial gene, cytochrome c oxidase I (COI), individuals collected from across the distribution of P. atomaria were investigated for haplotype diversity and levels of mitochondrial divergence. 3 Within P. atomaria, genetic distance averaged 0.5% across 23 unique haplotypes for 93 individuals, with an average of 14% difference between P. atomaria and the outgroup species, Paropsis obsoleta. Significant genetic structure was observed relative to geographical distribution, but not with respect to host plant species of origin. Greatest divergence was between the southern‐most sample site (Canberra) and northern sites in New South Wales and Queensland, indicating reduced gene flow between these regions. 4 Individuals from across eastern Australia belong to the same genetic species with population substructuring evident. Consequently, there is no evidence to suggest cryptic species complexes exist within the currently defined taxon. Continued implementation of control strategies for P. atomaria across its distribution is appropriate.     

Comparative phenology and growth of four Cenchrus ciliaris L. accessions established under arid bioclimate in Tunisia

A phenological study is one of the first steps in understanding the function of ecosystems. This is because phenological events reflect the way in which the species exploit the so‐called favourable periods in order to gain carbon and to allocate photosynthetic products for growth and reproduction. The objective of the present work was to examine the phenology of reproduction and the above‐ground growth of several Cenchrus ciliaris accessions, growing under the arid bioclimate in Tunisia. These accessions collected in the south of Tunisia are: Bou Hedma (P1), Tozeur (P2), Raas Jedir (P3) and Sidi Toui (P4). It was demonstrated that an important phenological variability exists within the different accessions studied. The statistical analysis (correlation and principal component analysis) showed that the accession from Bou Hedma (P1) was the most precocious and vigorous one.