Sinos Giokas - Profile on Academia.edu (original) (raw)

Papers by Sinos Giokas

Effects of abiotic factors on eggs’ dimensions of Cory’s Shearwater in a southern Ionian colony

Numerous studies of the factors affecting egg size in Procellariiformes have been conducted and h... more Numerous studies of the factors affecting egg size in Procellariiformes have been conducted and have proved very informative about their breeding ecology. Here we present the first results concerning the correlations between abiotic factors (orientation of nest entrance, type of nest, humidity and temperature in the nest) with egg dimensions (length, width and weight) of Cory’s Shearwaters (Calonectris diomedea diomedea) on the Stamfani Island colony. Fieldwork was carried out in June 2011, during the early stages of laying so as to minimize the bias on the egg weight measurements. A total sample of 30 eggs laid in different sub-colonies of the island were examined and length, width and weight scores (mean ± s.d.) were estimated at 6.75 ± 0.19 cm, 4.55 ± 0.14 cm and 76.40 ± 4.70 grams respectively. The aforementioned results enhance previous findings that support morphometric differences between the Atlantic and the Mediterranean Cory’s Shearwater subspecies. In addition significant...

Diversity, 2012

Our aim was to investigate species co-occurrence patterns in a large number of published biotic c... more Our aim was to investigate species co-occurrence patterns in a large number of published biotic communities, in order to document to what extent species associations can be found in presence-absence matrices. We also aim to compare and evaluate two metrics that focus on species pairs (the 'natural' and the 'checkerboard' metric) using also artificial matrices. We applied the two metrics to many data sets from a huge variety of insular systems around the world. Both metrics reliably recover deviating species pairs and provide similar, albeit not identical, results. Nevertheless, only a few matrices exhibit significant deviations from random patterns, mostly vertebrates and higher plants. The benchmark cases cited in literature in favor of such assembly rules are indeed included in these exceptional cases. In conclusion, competitive or cooperative species interactions shaping communities cannot be inferred from patterns exhibited by presence-absence matrices. When such an analysis is attempted though, both the 'natural' and the 'checkerboard' metric should be set in a proper framework in order to provide useful insights regarding species associations. A large part of the discussion on species co-occurrence had originally been based on a few exceptional data sets that are not indicative of general patterns.

GPS tracking of the foraging strategy of Scopoli’s Shearwater Calonectris diomedea in the Ionian Sea

Nowadays, modern telemetry tool give information of high level of accuracy regarding seabird fora... more Nowadays, modern telemetry tool give information of high level of accuracy regarding seabird foraging movements at sea. Here we report the first data of tracked breeding Scopoli’s Shearwaters (Calonectris diomedea) during the early stages of chick rearing period on one of the Strofades islands (southern Ionian Sea). Global Positioning System (GPS) loggers (20g, <5% of the bird’s body mass) storing tracking information were used on 18 breeders between 2011 and 2012. A total number of 12 individual foraging trips of varying degrees of completeness were obtained, showing a success rate of up to 67% per deployment. The stored tracks revealed that the majority of Scopoli’s Shearwaters made short foraging movements for food provision to their chicks which lasted one day. Spatial analysis of recordings showed that breeders use mainly four to five different foraging areas in western Peloponnese and Zakynthos island. The study provides also possible explanations of the tracked foraging ac...

Between‐island compositional dissimilarity of avian communities

Ecological Research, 2014

Compositional dissimilarity patterns of biotic communities can vary among different types of insu... more Compositional dissimilarity patterns of biotic communities can vary among different types of insular systems and among taxa with different dispersal abilities. In this work we examined compositional dissimilarity patterns of four avian groups, namely birds of prey, waterbirds, seabirds and landbirds, in various insular systems around the world. Compositional dissimilarity of avian communities was calculated for 25 presence‐absence matrices compiled from the literature. We used generalized linear mixed‐effects models to check for differences in between‐island compositional dissimilarity among the aforementioned avian groups that differ in their dispersal abilities, as well as between two different types of insular systems, oceanic and continental shelf. In agreement with our original hypothesis, landbirds which have relatively poorer dispersal abilities than birds of prey and waterbirds, exhibit higher between‐island compositional dissimilarity compared to these two avian groups. On ...

Mediterranean Marine Science, 2013

A significant number of studies worldwide have shown that incidental catches (by-catch) of seabir... more A significant number of studies worldwide have shown that incidental catches (by-catch) of seabirds in fishing gear might pose a considerable risk for the conservation of their populations. Nevertheless reliable data on by-catch rates of seabirds in European marine ecosystems are patchy and need to be improved. This study constitutes a first attempt at the evaluation of by-catch rates in the southern Ionian Sea. Data were obtained by distributing a specific questionnaire to the fishers of Zakynthos Island. 150 professional fishers (representing 90% of the local fishing fleet) participated in the research, and were interviewed during July-December 2010. The information collected showed that commercial longline and (to a lesser extent) gillnet fishery gears caused incidental catches mostly of Scopoli’s Shearwater and Mediterranean Shag. The temporal analysis of the incidental bird mortality showed that seabirds were more susceptible to be trapped in fishery gears set around sunrise du...

Census of total and breeding population of Scopoli’s Shearwater (Calonectris diomedea) colony on Strofades islands (Ionian Sea, Greece)

ABSTRACT Strofades Islands (37° 15’ N, 21° 00’ E) host a significant Scopoli’s Shearwater (Calone... more ABSTRACT Strofades Islands (37° 15’ N, 21° 00’ E) host a significant Scopoli’s Shearwater (Calonectris diomedea) colony, the largest in Greece. The total population on these two small islands (Stamfani and Arpyia), was estimated via coastal surveys by counting rafts which can comprise thousands of birds, 1-2 hours before dawn. Fieldwork involved three teams working simultaneously during the breeding seasons of 2009 and 2013. Total population size was estimated to be between 17,000 to 18,000 individuals whereas the population density on Stamfani and Arpyia were 3,068 inds and 2,723 inds per km of suitable nesting coastline respectively. The survey of the breeding population was based on assessing the Apparently Occupied Sites (AOS) in 30 square sampling units of 100 m2 each. Stratified sampling was made in 2009 after two nesting habitats of different quality were identified. The total breeding population was estimated from the density of nests (average over the sample units) and the size of the suitable nesting habitat of the colony, and was found about 5,587 pairs (C.I. 95%: 3,518 – 7,649), 3,585 pairs of which (C.I. 95%: 2,256 – 4,909) were on Stamfani Isl. and 2,002 pairs (C.I. 95%: 1.262 – 2.740) on Arpyia Isl.

A biogeographical analysis of Greek Oniscidean endemism

ABSTRACT Despite our incomplete knowledge of Greek Oniscidea, a great number of species have alre... more ABSTRACT Despite our incomplete knowledge of Greek Oniscidea, a great number of species have already been described, of which 69% are endemic. This unusually high percentage of endemics is a result of intense speciation triggered by the complex topography, paleogeography, and ecological history of Greece. Using 100 × 100 km Universal Transverse Mercator (UTM) squares as Operational Geographic Units (OGUs), we mapped the presence of all endemic species known until 1995, and applied Parsimony Analysis of Endemicity (PAE) in order to find patterns of OGU relationships. In the procedure, we reduced the original data matrix in two successive steps, excluding unin—formative and problematic species and OGUs. We analyzed separately the endemic species of the large genus Armadillidium, following the same procedure. The results lead to the recognition of two main biogeographic entities, the mountainous continental and the insular Aegean. These groups, and the relationships of OGUs on a finer scale, do not fully agr...

Journal of Molluscan Studies, 2014

Seasonal differences in the water content of four Codringtonia species were investigated using sp... more Seasonal differences in the water content of four Codringtonia species were investigated using specimens collected from the field. In addition, rate of water loss and expression of heat-shock protein 70 (Hsp70) were measured in a laboratory setting with six Codringtonia species subjected to a short-term heat shock. Using a phylogenetic framework, both the Hsp70 expression levels and the rate of water loss were investigated for their correlation with spatial and climatic variables. As indicated by the field-collected samples, during summer aestivation only C. helenae exhibited a tendency for water loss. During the short-term heat shock the rate of water loss in C. helenae was also significantly greater. No interspecific differences could be detected in the levels of Hsp70 in the species subjected to short-term heat shock. A single Codringtonia species seemed to maintain increased Hsp70 protein levels. In the species subjected to short-term heat shock, a positive relationship was found between Hsp70 levels and rate of water loss. On the other hand, the Hsp70 levels under normal conditions showed a negative correlation with altitude and mean summer precipitation of the sampling localities. Thus, species seem to adapt to harsher environmental conditions by maintaining higher levels of Hsp70.

Molecular phylogenetics and evolution, 2012

The aim of this work was to infer the phylogeny of the Greek endemic land-snail genus Codringtoni... more The aim of this work was to infer the phylogeny of the Greek endemic land-snail genus Codringtonia Kobelt 1898, estimate the time frame of the radiation of the genus, and propose a biogeographic scenario that could explain the contemporary distribution of Codringtonia lineages. The study took place in the districts of Peloponnese, Central Greece and Epirus of mainland Greece. Sequence data originating from three mtDNA genes (COI, COII, and 16S rDNA) were used to infer the phylogeny of the eight nominal Codringtonia species. Furthermore, the radiation time-frame of extant Codringtonia species was estimated using a relaxed molecular clock analysis and mtDNA substitution rates of land snails. The phylogenetic analysis supported the existence of six Codringtonia lineages in Greece and indicated that one nominal species (Codringtonia neocrassa) might belong to a separate genus distantly related to Codringtonia. The time frame of differentiation of Codringtonia species was placed in the L...

Amphibia-Reptilia, 2014

Two slow worm species are distributed at the southernmost part of the Balkan Peninsula: Anguis ce... more Two slow worm species are distributed at the southernmost part of the Balkan Peninsula: Anguis cephallonica, an endemic of the Peloponnese and the islands Zakynthos, Ithaki and Kephallonia, and A. graeca. Here, we investigate the intraspecific genetic diversity of A. cephallonica from the Peloponnese and Kephallonia and analyse A. graeca, from the northern Peloponnese, where it is found in sympatry with A. cephallonica. MtDNA and nDNA phylogenetic analyses confirm the genetic similarity of Peloponnesian and Kephallonian populations of A. cephallonica and reveal significant mtDNA genetic variation within it, probably related to the occurrence of multiple subrefugia in the Peloponnese. Peloponnesian A. graeca populations are genetically similar to non-Peloponnesian conspecifics implying recent dispersal to the Peloponnese. In contrast to the genetic markers, morphological characteristics (such as the number of mid-body scale-rows) failed to distinguish between Peloponnesian A. cephall...

Molecular Phylogenetics and Evolution, 2007

Mitochondrial DNA sequences from 16S rRNA and ATPase8 genes were used to investigate phylogeograp... more Mitochondrial DNA sequences from 16S rRNA and ATPase8 genes were used to investigate phylogeographic patterns of the land snail Albinaria (Gastropoda: Clausiliidae) in the Aegean archipelago. Forty-two populations of Albinaria were analyzed, mainly A. turrita, A. caerulea and A. brevicollis, collected from 22 Aegean islands and certain surrounding regions. Maximum parsimony, maximum likelihood and Bayesian analyses on 16S rRNA and combined datasets produced trees that share signiWcant similarity and reveal a phylogeny with distinct branches which are in general, but not full, agreement with current taxonomy. The Aegean taxa are not monophyletic as a whole, since A. turrita does not cluster with A. caerulea and A. brevicollis. The latter form a distinct monophyletic cluster, within which two groups are evident. These groups do not readily correspond to currently accepted morphospecies; one contains the populations that inhabit the central part of the archipelago plus some eastern islands, while the other contains populations whose geographic distribution is restricted to the southeastern part of the archipelago. The divergence between these two groups is attributed to vicariance events that primarily shape contemporary distributions. Although dispersal may also be present, certain small-and large-scale vicariance events can be traced; alternative phylogeographic hypotheses are discussed in view of the historical biogeography of the region.

PLoS ONE, 2014

Drilus beetle larvae (Coleoptera: Elateridae) are specialized predators of land snails. Here, we ... more Drilus beetle larvae (Coleoptera: Elateridae) are specialized predators of land snails. Here, we describe various aspects of the predator-prey interactions between multiple Drilus species attacking multiple Albinaria (Gastropoda: Clausiliidae) species in Greece. We observe that Drilus species may be facultative or obligate Albinaria-specialists. We map geographically varying predation rates in Crete, where on average 24% of empty shells carry fatal Drilus bore holes. We also provide first-hand observations and video-footage of prey entry and exit strategies of the Drilus larvae, and evaluate the potential mutual evolutionary impacts. We find limited evidence for an effect of shell features and snail behavioral traits on inter-and intraspecifically differing predation rates. We also find that Drilus predators adjust their predation behavior based on specific shell traits of the prey. In conclusion, we suggest that, with these baseline data, this interesting predator-prey system will be available for further, detailed more evolutionary ecology studies.

Scolopendra cingulata Latreille, 1829 is the commonest scolopendromorph species in the Mediterran... more Scolopendra cingulata Latreille, 1829 is the commonest scolopendromorph species in the Mediterranean area. However, its morphological and geographic variation has not been examined so far, and therefore robust hypotheses about the factors that have shaped that variability are lacking. We examined, using multivariate methods for 19 morphometric and meristic characters, the morphological variation of that species using a comprehensive sample of 503 adult specimens from 130 restricted geographic localities. The localities were distributed in three major geographic areas (Balkans, Asia Minor-Middle East, and Italy) in order to discern biological entities and to estimate the morphological relationships between populations and geographic regions. Results showed significant differences between the three geographic groups. Characters such as the distance between the paramedian sulci of the 7th and 8th tergite, the number of antennal segments, the number of spines on the dorsal side of 21st prefemur and number of spines on the 21st prefemoral process significantly discriminated populations of S. cingulata along a west-east geographic gradient. Both eastern (Balkan) and easternmost populations (Asia Minor-Middle East) showed higher mean values of antennal articles and spines of 21st prefemur than the Italian populations. No significant morphological variation was discovered between the sexes of S. cingulata apart from cephalic width and distance between the two paramedian sulci of the 7th and 8th tergite. Based on certain morphometric differences among the three major geographic regions, we suggest that S. cingulata originated in the east and colonized south European area from two different geographic routes. It is suggested that west-east morphological trend of S. cingulata is related either to the prominent palaeogeographic events of the area or to the competition with S. oraniensis Lucas, 1846 in the western Mediterranean.

Mitochondrial phylogeography, intraspecific diversity and phenotypic convergence in the four‐lined snake (Reptilia, Squamata)

Zoologica Scripta, 2013

The four‐lined snake, Elaphe quatuorlineata, has a fragmented distribution, restricted in contine... more The four‐lined snake, Elaphe quatuorlineata, has a fragmented distribution, restricted in continental regions and islands of the Italian and Balkan peninsulas, and includes several morphologically described subspecies. In this study, mtDNA sequences are used to investigate its evolutionary and biogeographical history, to explore the role of palaeogeography, palaeoclimate and human activities in shaping the observed phylogeographical patterns and to discuss whether current subspecific taxonomy is consistent with the intraspecific phylogeny. The phylogeography of the species is a result of both vicariant and dispersal events, some of them transmarine and even human mediated. Its diversification began approximately 3.5 Mya and continued during the Pleistocene glacial periods, when the four‐lined snake's range was restricted in the Italian and Balkan peninsulas, and subsequently expanded from subrefugia, which acted as ‘biodiversity pockets’. Our study supports the recognition of th...

Waterbirds, 2013

The absence of juvenile sexual dimorphism in birds often impedes sex determination using external... more The absence of juvenile sexual dimorphism in birds often impedes sex determination using external morphology. We examined sex ratio variation in Scopoli's Shearwater (Calonectris diomedea) fledglings (n = 135) on a Strofades island (southern Ionian Sea) between 2007 and 2011. We determined sex by using a polymerase chain reaction-based methodology on blood samples. The molecular technique revealed a slightly male-biased sex ratio (52.6%) during the five consecutive breeding seasons. In addition, morphological analysis using six morphometric variables (bill length, bill width, nalospi, bill-head length, head length, tarsus length) and body weight indicated that males were significantly larger than females for all the tested variables. The combined use of those variables correctly classified 81.2% of known-sex fledglings, and the stepwise discriminant analysis pointed out that bill length was the most discriminating variable followed by bill depth, head length, and body weight.

Molecular Phylogenetics and Evolution, 2013

The majority of the family Typhlopidae occurs in the Neotropic, Australasian, Indo-M alayan and A... more The majority of the family Typhlopidae occurs in the Neotropic, Australasian, Indo-M alayan and Afrotropic ecoregions. They show a restricted distribution in the western Palearctic, where they include few native species, i.e. Rhinotyphlops simoni , R. episcopus and Typhlops vermicularis . A unique species among typhlopids is T. socotran us, found in Socotra, one of the most endemic-rich archipelagoes. In this study we determine the phylogenetic position of the above mentioned species and discuss their systematics, origin and biogeograph y. For this purpose we use three protein-coding nuclea r markers (AMEL-amelogenin, BDNF-brain-derive d neurotrophic factor and NT3-neurotrophin 3) to construct a time-calibrated phylogeny of the family Typ hlopidae. Our results show that T. socotranus is a sister-species to T. vermicularis, while R. simoni and R. episcopus are sister-sp ecies to each other and are found within the African clade of the family, although they are geographi cally distributed in west Asia. Additionally we discuss several hypotheses on their origin, as well as the occurence of typhlopids in Eurasia.

Molecular Phylogenetics and Evolution, 2012

Typhlops vermicularis is the only extant scolecophidian representative occurring in Europe. Its m... more Typhlops vermicularis is the only extant scolecophidian representative occurring in Europe. Its main distribution area, the eastern Mediterranean, has a complicated geological and climatic history that has left an imprint on the phylogenies and biogeography of many taxa, especially amphibians and reptiles. Since reptiles are sensitive indicators of palaeogeographical and palaeoclimatic events, we investigated the intraspecific genealogy of T. vermicularis in a phylogeographical framework. A total of 130 specimens were analyzed, while the use of formalin and ethanol as preservatives called for a special treatment of the samples. Partial sequences of two mitochondrial (12S and ND2) and one nuclear (PRLR) marker were targeted and the results of the phylogenetic analyses (NJ, ML and BI) and the parsimony-network revealed the existence of 10 evolutionary significant units within this species. In combination with the results of the dispersal-vicariance analysis, we may conclude that the Eurasian blindsnake has encountered a sequence of extinction events, followed by secondary expansion from refugia. Estimation of divergence times showed that severe climatic changes between significantly wetter and drier conditions in the Late Neogene have played a key role on the evolutionary and biogeographical history of T. vermicularis. Additionally, both markers (mtDNA and nDNA) distinguished a largely-differentiated evolutionary lineage (Jordan and south Syria), which could even be reckoned as a full species. Our study reveals the existence of cryptic evolutionary lineages within T. vermicularis, which calls for further attention both on the protection of intraspecific varieties and the respective geographic areas that hold them.

Journal of Molluscan Studies, 2005

We examined the seasonal patterns of physiology and biochemical composition in the rock-dwelling ... more We examined the seasonal patterns of physiology and biochemical composition in the rock-dwelling clausiliid land snail Albinaria caerulea in relation to its ecology, morphology and climatic data. We found that A. caerulea displayed significant seasonal changes in biochemical composition and enzyme activity, especially during aestivation. Sugars were catabolized early in aestivation, and proteins and lipids seem to be the primary metabolic substrates after sugar reserves were depleted. Atypical for aestivating land snails was the accumulation of lactate and LDH during the first weeks of aestivation, possibly suggesting that anaerobic pathways can provide additional energy. Moreover, mortality was not significantly higher during aestivation, fresh-mass differences between the aestivation and active period were not substantial and the rate of fresh-mass decline during aestivation was low. In addition, A. caerulea shows a series of morphological (thick white shell, strengthened and reflected apertural lips, thick epiphragm, internal lamellae, door-like clausilium) and behavioural (high aggregation) characteristics that support survival during adverse climatic conditions by preventing desiccation. We did not find a correlation of biochemical variables (except LDH) with climatic conditions. Yet, the biochemical variables, taken as a whole, are sufficient to distinguish the periods of aestivation and activity. The above suggest that the start of aestivation is primarily controlled by an endogenous component, and perhaps changes in the biochemical composition are a by-product of this component and not a direct response to climatic conditions. These results, in conjunction with the non-elevated mortality during aestivation, indicate that in this Albinaria population morphological, behavioural and physiological adaptations to the dry conditions of the climatically unpredictable Mediterranean-type ecosystems are in effect, and seem to ensure sufficient water and fuel reserves.

Mitochondrial Dna and Morphological Differentiation of Albinaria Populations (Gastropoda: Clausiliidae)

Journal of Molluscan Studies, 1995

ABSTRACT Albinaria , despite its restricted geographical distribution, exhibits an extreme degree... more ABSTRACT Albinaria , despite its restricted geographical distribution, exhibits an extreme degree of differentiation. The use of conventional or numerical taxonomy has not facilitated the understanding of evolution of the genus. Twelve populations belonging to four species were studied with a combined approach using mitochondrial DNA (mtDNA) and qualitative morphological data. The complete mtDNA genome of A. coerulea from Amorgos island was cloned and used in mtDNA restriction site analysis of the other populations. Maximum parsimony cladistic analysis of nine populations provided trees sharing the same basic topology. Certain restriction sites and morphological characters appear to be species specific, while incongruity is observed at the intraspecific level. Sequence divergence and the paleogeographic history of the area were used for construction of an evolutionary scenario and a rough estimation of the Albinaria mtDNA clock.