Robert A. D. Cameron

Citizen Science Reveals Unexpected Continental-Scale Evolutionary Change in a Model Organism

Organisms provide some of the most sensitive indicators of climate change and evolutionary responses are becoming apparent in species with short generation times. Large datasets on genetic polymorphism that can provide an historical benchmark against which to test for recent evolutionary responses are very rare, but an exception is found in the brown-lipped banded snail (Cepaea nemoralis). This species is sensitive to its thermal environment and exhibits several polymorphisms of shell colour and banding pattern affecting shell albedo in the majority of populations within its native range in Europe. We tested for evolutionary changes in shell albedo that might have been driven by the warming of the climate in Europe over the last half century by compiling an historical dataset for 6,515 native populations of C. nemoralis and comparing this with new data on nearly 3,000 populations. The new data were sampled mainly in 2009 through the Evolution MegaLab, a citizen science project that engaged thousands of volunteers in 15 countries throughout Europe in the biggest such exercise ever undertaken. A known geographic cline in the frequency of the colour phenotype with the highest albedo (yellow) was shown to have persisted and a difference in colour frequency between woodland and more open habitats was confirmed, but there was no general increase in the frequency of yellow shells. This may have been because snails adapted to a warming climate through behavioural thermoregulation. By contrast, we detected an unexpected decrease in the frequency of Unbanded shells and an increase in the Mid-banded morph. Neither of these evolutionary changes appears to be a direct response to climate change, indicating that the influence of other selective agents, possibly related to changing predation pressure and habitat change with effects on micro-climate.

Land Snail Faunas in Polish Forests: Patterns of Richness and Composition in a Post-Glacial Landscape

ABSTRACT We examine variation in species richness, species composition and distance decay in similarity in forest snail faunas from Poland and a small part of Transcarpathian Ukraine, and their connection with geographical position in relation to Pleistocene refugia. Forest faunas were sampled from sites of standard size in each of ten regions. Data were analysed using DCA and partial CCA, extracting the geographical, climatic and ecological correlates with the major axes. Relationships among site and regional faunas were further examined through the Simpson Index of Similarity. Site species richness shows no significant variation with geographical position or climate, but relates to soil and vegetation characteristics. Composition varies with location; southern highland faunas differ from one another far more than do northern lowland faunas, showing a clear east-to-west pattern of change. The aggregate highland fauna is richer than that of the lowlands, which is a subset of the former. Two intermediate upland regions show different associations, one with the highlands the other with the lowlands. Lowland faunas, even over large distances, are very similar, and all relate more closely to the western end of the highlands than to the east. Disaggregating the fauna into large and small species shows that the former show a stronger geographical pattern than the latter; most universally distributed species are small. Latitudinal variation in regional richness, and longitudinal differentiation among highland faunas relate to distance from glacial refugia. This is not reflected in site species richness, raising questions about the assembly rules for local faunas. The western bias in the relationships of lowland faunas to those of the highlands, the differences between large and small species and the varying rates of faunal turnover within the area studied suggest that patterns of post-glacial dispersal are complex and incompletely understood.

Fossil evidence of recent human impact on the land snail fauna of Madeira

The Madeiran islands, located at 33?N in the eastern Atlantic, were colonized early in the 15th century, and perhaps up to a century earlier. The woodland and scrub cover was rapidly reduced and the amount of grassland and dis- turbed ground increased. The effect on the land snail popu- lation has been assessed by analysis of fossil assemblages from a deposit in eastern Madeira. Dates were obtained by measurement of amino acid epimer ratios (D-alloisoleucine/L- isoleucine) of individual shells, calibrated against radiocarbon- dated samples. Because this method allows dating of individual shells, it was possible to reconstruct the chronology of various species from mixed-age assemblages. It also per- mits dating of shells too young for radiocarbon dating (post- AD 1650). Fifteen land snail assemblages were analysed from deposits of post-settlement age (c. 420-50 yr BP). Of the thirty-four species of land snails present in the samples, nine have become extinct over the period. In contrast, only five species became extinct on the island during the previous c. 300,000 years. The majority of the extinctions have occurred within the last two centuries, as a result of habitat destruction. A major decline in the abundance of woodland species took place during the 20th century. The extinction of the endemic Caseolus bowdichianus, abundant in middle Holocene de- posits, occurred about a century after colonization of the island. Theba pisana, a snail of similar size and shape, was introduced around the time of colonization, and is now abun- dant in grassy areas. Two endemic grassland species, Discula polymorpha and Heterostoma paupercula, have also become more abundant and thus apparently benefited from the arrival of man.

The Quaternary eolian sequence of Madeira: stratigraphy, chronology, and paleoenvironmental interpretation

A thick (ca. 40 m) sequence of coastal eolian sediments occurs on a narrow peninsula on the eastern end of the island of Madeira, located in the Eastern Atlantic at 33°N latitude. The sediments consist of black volcanic sands (with or without bioclasts) as well as clay units up to 2 m thick. A series of inceptisols (Eutrochrepts) and one alfisol (a Hapludalf) are developed in these sediments. Land snail shells and secondary carbonates, in the form of well-developed rhizoliths, calcretes, fissure-fills, and soil nodules, are present in abundance. The chronology of the sequence was determined by 14C and UTh analyses of land snail shells and secondary carbonates and amino acid epimerization analysis of land snail shells. All sediments, including the clay units, are originally of eolian origin, derived from the beach to the south of the deposit, but some have been redeposited by colluviation. Temporal variation in the lithology of the sediments relates to variations in sea-level, with black sands being deposited during lower sea level stands and clays at the lowest. It is suggested that fine marine sediments, exposed during low sea-level stands, may also be the dominant source of silty or clayey units in other coastal eolian deposits in the subtropical Atlantic and Mediterranean. The sequence spans from 200,000–300,000 years ago up to the 20th century. Sedimentation was discontinuous and often rapid; erosional hiatuses are present. During the Holocene, eolian sands started accumulating at 8200 yr B.P. during a transgressive phase and stopped at 4500 yr B.P. as sea level approached its present height. Colluviation increased dramatically following the first human settlement of the island in the 15th century and continued up to the 20th century, as dated by amino acid epimerization analysis of land snails. Earlier periods of colluviation were identified from the age distribution of land snail shells redeposited in younger colluvium. Paleoenvironmental reconstruction was based mainly on soil and sediment features (including rhizolith morphology) and land snail faunas but also on stable isotope variations (13C, 18O) in land snails and secondary carbonates, pollen (generally not well preserved), and phytoliths. Most of the portion of the Middle Pleistocene represented in the sequence was characterized by moderately dry conditions, in comparison to the late Pleistocene and Holocene. During the last interglacial, relatively wet conditions occurred, wetter than during the Holocene interglacial. Moderately moist conditions were present during the accumulation of the thick unit dating to ca. 80,000 yr B.P. As sea level fell subsequent to this period, conditions appear to have become drier. Starting ca. 50,000–55,000 yr B.P., conditions were especially wet, but prior to the last glacial maximum, markedly arid conditions ensued. Toward the end of the last glacial, wet conditions returned and produced the best-developed soil preserved in the sequence. Moderately moist conditions occurred during the early to middle Holocene but apparently become slightly drier after 4500 yr B.P. The impact of human settlement can be seen in the loss of woody vegetation and enhanced gullying and colluviation during the last ca. 500 years.

FOREST SNAIL FAUNAS FROM S. E. QUEENSLAND AND N.E. NEW SOUTH WALES (AUSTRALIA): PATTERNS OF LOCAL AND REGIONAL RICHNESS AND DIFFERENTIATION

While regional snail faunas of low-latitude regions tend to be richer than similar areas at high latitude, there seems to be little difference between site (e.g. < 400 m2) richness, which often ranges between 20 and 40 species across a wide latitudinal range. Given this seeming paradox, it is surprising how little investigation has been made into how land snail species are packed into the tropical landscape across multiple scales. This paper addresses this question by analyzing faunal lists from six regions spread across a 550 km extent in the temperate rain forests of eastern Australia. Considerable heterogeneity was observed both within similar habitat types within (ca. 40–60% faunal similarity) and between (ca. 10–50%) different regions. The Charopidae constituted the largest fraction of the fauna (up to 70% of species), and were thus responsible for most of the variation in composition. While the number of species per region (ca. 30–50) was broadly comparable to Europe and North America, the rate of faunal turnover with distance was found to be 2–30 times greater. While geographic turnover in European and North American faunas is largely driven by large species, in eastern Australia turnover was largely driven by small, litter-dwelling species that tend to be unique to each region. The comparative richness of the eastern Australian fauna is thus largely related to evolutionary processes that have caused divergence at regional scales, rather than increased niche-packing or syntopic diversity at site scales.

At the north-eastern extremity: variation in Cepaea nemoralis around Gdańsk, northern Poland

Variation in the shell colour and banding polymorphism in the land snail Cepaea nemoralis was studied in 260 populations in the region of Gdańsk, northern Poland. Unlike in other regions of Poland, many populations contain brown shells. Populations from shaded habitats have higher frequencies of brown than those from open and intermediate habitats, largely at the expense of yellow shells. Nearly all brown shells are also unbanded. Apart from this disequilibrium, banding morphs among yellow and pink shells show no relationship to habitat. There are no broad geographical trends in morph-frequencies, but there are very strong correlations among populations very close together, revealed both by pairwise analysis and Moran’s I. Principal Component Analyses show that these correlations relate to overall genetic similarity at the loci involved. The populations are at the north-eastern limits of the species’ range; habitats are mostly anthropogenic, and comparisons with studies in two urban areas (Wrocław, SW Poland, and Sheffield, central England) suggest that the patterns of variation seen are a product of human transport of propagules followed by local dispersal. The effect of habitat here is much less marked than in regions much further west, but it indicates that natural selection has occurred.

Mollusc communities in Bulgarian fens: predictive power of the environment, vegetation, and spatial structure in an isolated habitat

Mollusc communities of previously unexplored Bulgarian fens were studied in order to determine and generalise the patterns of species richness and composition along the mineral richness gradient. The aim was also to compare predictive values of the environment, vegetation and spatial structure. Altogether, 44 mollusc species were recorded at 40 treeless fen sites. Species richness varied from 0 to 18 species per site, and it was positively associated with the mineral gradient and negatively with altitude. However, the best predictor was obtained using plant species composition. All explanatory variables had higher effect on land snails than on the entire mollusc assemblage (including aquatic species). Species richness and abundance were significantly and positively correlated with the species composition turnover; the communities were highly nested, with poor sites having subsets of the fauna found in the richest. The main direction of mollusc species turnover was highly associated with that observed for vegetation, and the main gradient of plant species composition was able to explain nearly 20% of total variation in mollusc data. We found that spatial structure explained by far the highest proportion of independent variation, which reflected the high level of geographical isolation of Bulgarian fens and regional differences independent of any environmental variation. Our results demonstrate (1) the general role of mineral richness gradient for structuring mollusc communities in fens, (2) the pivotal indicator role of plant species composition in predicting species composition of mollusc communities, despite being trophically independent and (3) the effect of isolation and origins of the habitat on species composition: most species have wide geographical distributions within the habitat type, and geographical patterns within Bulgaria may have a stochastic element.

FOSSIL LAND SNAIL FAUNAS OF PORTO SANTO, MADEIRAN ARCHIPELAGO: CHANGE AND STASIS IN PLEISTOCENE TO RECENT TIMES

Samples of fossil land snails were made at 14 sites on the island of Porto Santo, Madeiran archipelago. Material in stratigraphical sequences could be dated by A/I racemization calibrated against radiocarbon dating, and against Uranium/Thorium estimates based on Madeiran material. Although errors associated with the oldest samples are large, it is clear that the oldest shell-bearing deposits are at least 300 ka old, and probably much older. Some taxonomic difficulties have been resolved by morphometric studies. The geographical pattern in the fossils (in both faunal composition and morphometrics) resembles closely that seen today, the southwest of the island being particularly distinctive. Of 58 native taxa found in the deposits, 22 are extinct on the island, though four still survive on Madeira. Extinction has been greater in the southwest than elsewhere, and early fossil faunas there are richer than later ones. As on Madeira, more than half of this extinction seems likely to be the consequence of human disturbance, which has also reduced and fragmented the ranges of other species. The overall pattern is of distributional stasis in many species, reduction of range or extinction in many others, but very few cases of range expansion. Neither extinctions nor changes in apparent abundance can be related to known changes in global climate over the period involved. This relative stasis is in marked contrast to the situation on Madeira, only 40 km away, where there are temporal shifts in the fauna, and evidence of colonization events. Possible reasons for this difference are discussed.

CHECKLISTS, SYSTEMATICS AND THE CLECOM INITIATIVE: AN ALTERNATIVE VIEW FROM EUROPE

Davis (2004) raised important issues about the function and construction of species checklists, and, by way of examples, provided a critique of two recent lists produced in Europe: the CLECOM I list for the land and freshwater Mollusca of northern, Atlantic and central Europe (Falkner et al., 2001), and the more detailed list for France alone (Bouchet, 2002; Falkner et al., 2002). It may be noted that CLECOM I is accompanied by CLECOM sections I and II (Bank et al., 2001), which provides a supraspecific classification for a larger area, including the whole of Europe, Turkey and Macaronesia. His critique provoked two responses from the authors (Bouchet, 2006; Bank et al., 2006). In the first of these, some differences of opinion are thought to reflect the impact of real differences in the degree and character of taxonomic differentiation in regional faunas on thought and practice, while in the second the authors suggest that Davis is privileging molecular taxonomy at the expense of the use of morphological characters. The reference by Davis (2004) to the notorious “Nouvelle Ecole” of Bourguignat and his followers (Dance, 1970), in particular, is seen as provocative and unjustified. We note that a significant part of these arguments relate as much to the principles and procedures of classification as to the function and content of checklists as such. Both Davis and his respondents raise general and more specific issues; the latter are mainly concerned with details of work on particular freshwater groups. As workers mainly on terrestrial molluscs, we do not intend to enter into those debates. We believe, however, that the general issues are of significance to the malacological community, and there is a danger that arguments about such lists could become very parochial, reinforcing the rather negative image that tarnishes taxonomists generally. At the extreme, they could provide MALACOLOGIA, 2006, 49(1): 225−230

The 17th World Congress of Malacology

The 17th World Congress of Malacology was held from the 18th to the 24th of July 2010, in Phuket Town (Island of Phuket, Thailand). It was the first time the Congress was held in Asia, and not long before the Congress we were not sure if we would ever get there, because of the political unrest in Thailand in the spring of 2010. However, our Thai colleagues kept promising that everything would be all right, and in the end everything was more than all right. The Congress venue was the Royal Phuket City Hotel, big enough to accommodate all of us; it had lots of conference rooms as well, where all the sessions were held. In the hotel lobby, just before you entered the conference rooms, there were two Congress mascots (Figs 1, 2): two Thai endemics, very beautifully made, complete with identification labels, and very big: when you stood next to one of them, assuming you were medium height, the tentacles reached to your shoulder. The Congress fee was very reasonable, considering that it included not only the two receptions, plus very reception-like poster session, but also lunches during the sessions. Every participant was given a Congress bag, tickets for all the receptions, lunch tickets and – of course – abstract volume which, by the way, was very heavy and contributed to the weight of our luggage when we were going home. The day before the Congress sessions started (July 18th, Sunday) there was the icebreaker reception, at the Kata Beach Resort & Spa, a very nice and posh hotel on the seaside. Mind you, malacologists are a sociable lot, they hardly need to break ice, but they like receptions a lot, and this one was lots of nice booze and nice snacks. We hardly had time to recover and then, on Tuesday (20th) we had the poster session which was a reception rather than poster display: booze and lots of very special little snacks, so that very many people went foraging among the food and drink stalls instead of staying at their posters. Wednesday (21st) was (quite sensibly) a day off: people could either go to the Congress excursion, or do whatever they liked. The sessions continued on the 22nd and 23rd. The farewell dinner on the evening of the 23rd was held at the same hotel as the icebreaker (Fig. 3). The food was great, the drinks too, there was a folk group performing (Fig. 4), and the authors of the best student posters and presentations were given prizes. The official conference trip went to the Marine Biological Center, the Phuket Aquarium, and the Sea Shell Museum. The Marine Biological Center carries out numerous research and educational tasks. One of them is the breeding of rare and vulnerable species for aquaria and reintroductions. We were shown the large-scale nurseries of various species of turtles and fish (Figs 5–8), including sea-horses and sharks. Among the Phuket Aquarium creatures, the most impressive were the giant groupers (Epinephelus lanceolatus), the largest reef-dwelling fish in the world. Giant they are, reaching almost 3 m and weighing up to 600 kg. The species is listed in the IUCN Red List as vulnerable because of exploitation. Groupers that are served in restaurants typically range in weight from 20 kg to 50 kg. Just before the Congress, a grouper over 2 m long and weighing 220 kg had been caught and sold to a restaurant in Singapore. This was featured on the first pages of the newspapers. The Straits Times we were handed out on a plane to Phuket called it “a monster fish” and detailed the various prized parts of the fish, including a 3 kg eyeball, throat and lips, ordered in advance by wealthy customers. How can a species be saved whose consumption is so glamorized by popular press? The Sea Shell Museum amazed us. The exhibition features more than 2,000 species, including the only left-handed noble volute (Cymbiola nobilis) ever found, a 250 kg shell of a giant clam (Tridacna gigas), 380 million-year-old fossils, and one of the worlds rarest golden pearls. Our personal favourites were however the xenophorids, marine snails whose name loosely translated from Greek means “carrying foreigners”. As the shell grows, the animal cements Vol. 19(2): 107–116