Polyploidy in Aconitum subgenus Lycoctonum (Ranunculaceae)

Chromosome numbers and morphology in 22 populations belonging to 11 taxa of Aconitum subgenus Lycoctonum (Ranunculaceae) from China were studied. Some taxa were diploid, with 2 n  = 16, but four species and two varieties were found to be tetraploid, with 2 n  = 32. They are concentrated in the Hengduan Mountains region in south-west China, indicating that polyploidy could have played an important role in the speciation of the subgenus in this region, one of the areas of the world with a high concentration of endemic species. The relationships of some of the species are discussed.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 343–353.     

Chromosomes of four species in three genera of Commelinaceae from China and their systematic implications

Chromosomes of four species in three genera of Commelinaceae from China were examined. Spatholirion longifolium had 2 n  = 20. This small genus is considered to be of a possible polyploid origin based on x  = 5, a basic number shared by its closest ally, the monospecific genus Streptolirion , with its only species having 2 n  = 10. The two genera were found to be very different from each other in their karyotypic constitution. The differences in both chromosome number (2 n  = 20 vs. 10) and karyotypic constitution support their separation as two independent genera. The remaining three species, Amischotolype hispida , Porandra ramosa and P. scandens , all had 2 n  = 36. In view of the occasional occurrence of 2 n  = 18 in the African Coleotrype , a genus very close to Amischotolype and Porandra in gross morphology, these three species are all very probably polyploid based on x  = 9. The high degree of karyotypic similarity of the three genera also strongly indicates their close affinity and supports their placement in the subtribe Coleotrypinae. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 399–403.     

Genetic diversity and structure of the cycad Zamia loddigesii Miq. (Zamiaceae): implications for evolution and conservation

The genetic diversity and structure of four populations of the cycad Zamia loddigesii were studied throughout its range in Mexico. Allozyme electrophoresis of 15 loci was conducted. The mean number of alleles per locus was 1.80 ± 0.09, the percentage of polymorphic loci was 66.6 ± 5.4, and the expected heterozygosity was 0.266 ± 0.02. The results indicated that the genetic diversity was relatively higher, with respect to tropical tree species and other cycads. The genetic variation explained by differences among populations was 18%. On average, gene flow between paired populations was similar ( Nm  = 1.6) to other tropical forest trees and cycad species. Our results indicated that the geographical isolation among populations of Z. loddigesii generated allele loss, as well as a clinal variation in the frequencies of two loci ( MDH and MNR2 ), in relation to the latitudinal distribution of populations. The populations have become fragmented due to increasingly higher pressure of habitat conversion and disturbance. The importance of the establishment of sanctuaries and protected areas and a reduction in deforestation is highlighted in this research as a way of preserving the high genetic diversity of this and other endemic species.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 533–544.     

Fitness, developmental instability, and the ontogeny of fluctuating asymmetry in Daphnia magna

Fluctuating asymmetry (FA) is the most commonly used measure of developmental instability. The relation between FA and individual fitness remains controversial, partly due to limited knowledge on the mechanisms behind variation in FA. To address this, we investigated the associations between FA, growth and reproduction as well as the ontogeny of FA in a clonal population of Daphnia magna . FA was not correlated with growth and reproduction, either at the between- or the within-individual level, in a high ( N  = 48 individuals) or in a low ( N  = 52 individuals) food-quantity regime. There were therefore no indications of functional effects of FA or of phenotypic trade-offs between developmental stability, growth and reproduction. Individual asymmetries varied randomly in sign and magnitude between subsequent molts ( N  = 19 individuals, 9–11 instars), but the levels of FA were generally lowest at intermediate ages. No feedback between right and left sides was detected. This suggests that FA only reflects the most recent growth history, that developmental instability may increase in old age, and that FA depends on processes operating on each side of the body independently. The results also suggest that FA differences within and among individual Daphnia are largely random, with limited biological significance.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 179–192.     

Intraspecific variation in segment number in Pachymerium ferrugineum (C. L. Koch, 1835) (Chilopoda: Geophilomorpha) in the south Aegean Archipelago (north-east Mediterranean, Greece)

Geophilomorph centipedes have numerous leg-bearing segments, always an odd number. Previous research has shown the significant role of latitudinal clines and temperature on intraspecific variation, supporting the view that species of geophilomorphs from cold and temperate regions tend to have fewer segments than those from warmer regions. Here, data are presented on segment numbers of Pachymerium ferrugineum (C. L. Koch, 1835) from the south Aegean Archipelago. Within the framework of a study of the centipede fauna of the south Aegean Islands, three adjacent geographical areas with discrete geological histories were studied (Crete, Cyclades, and Dodecanese). There is no evidence to indicate that a latitudinal trend is present across these three main geographical regions. Apart from Crete, there is no demonstration of a cline along the longitudinal axis of the Aegean. However, the insular characteristics of the central and south-east Cyclades could possibly support higher modal segment numbers. In addition, examination of males and females of P. ferrugineum confirmed the existence of latitudinal clines in certain cases among the islands of Crete, Cyclades, and Dodecanese.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 533–539.     

Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the 'living fossil'Sphenodon (Reptilia: Rhynchocephalia)

Tail autotomy and regeneration are less known in Sphenodon ('Reptilia': Rhynchocephalia) than in Squamata. We examined museum specimens, Sphenodon guntheri ( N  = 8) and Sphenodon punctatus ( N  = 172), wild Sphenodon punctatus ( N  = 19) and Sphenodon sp. skeletons ( N  = 8). In S. punctatus , unlike in typical Squamata, sexes had similar relative (intact) tail lengths, and regeneration frequencies; tail and body growth was isometric. Tail breakage was usually intravertebral, usually followed by ablation of a variably sized terminal vertebral piece, partly deviating from lizards. Hypothetically, imperfect autotomy results from sphenodon's primitiveness. As in squamates, tail-losers were morphologically more left-side dominant than tail-retainers. Individual directional asymmetries in digit morphology and in digit injury were correlated (in lizards observed only at population level); tail-losers had more fluctuating asymmetry but their exclusion did not facilitate morphological taxonomic distinctions (no 'Seligmann effect'). In S. punctatus , extents and directions of sexual dimorphism paralleled differences between tail-retainers and tail-losers, females resembling tail-losers, also accounting for character interdependence (developmental constraints; employing a method similar to phylogenetic contrasts). The variation in the location of tail injury was correlated with the continuum of variation between injured and intact (pholidotic) morphotypes. These last two phenomena remain to be explored in Squamates.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 721–743.     

Evolution of life history traits in Leporidae: a test of nest predation and seasonality hypotheses

Recently, it has been proposed that adult mortality schedules may be responsible for latitudinal patterns of life history variation in passerine birds, whereas nest predation only could explain within latitude patterns. Unfortunately, no independent test has been performed regarding the importance of nest predation with different taxa. In the present study, seasonality and nest predation hypotheses explaining variations in gestation time and litter size in 17 lagomorph species were tested. Among latitude patterns were analysed using the phylogenetic independent contrast method of Felsenstein and within latitude patterns were analysed by the pairwise comparative method. The results obtained indicate that latitudinal patterns observed in both variables are explained by different factors: seasonality for litter size and nest predation for gestation time. Litter size variations within latitudes are also explained by differences in nest predation, supporting previous hypotheses. In conclusion, the present study suggests that, when compared among latitudes, different life history traits (e.g. litter size and gestation time) may be shaped by different selective forces and that the effects of nest predation may be high both within and between latitudes.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 603–610.     

Chromosomal polymorphism in the Atlantic dog-whelk, Nucella lapillus (Gastropoda: Muricidae): nomenclature, variation and biogeography

Nucella lapillus appears to be unique within the Muricidae, and indeed the Mollusca, in exhibiting a Robertsonian chromosomal polymorphism. The recorded diploid values range from 2 n  = 26 to 2 n  = 36, putatively brought about by fusion of smaller chromosomes to form five pairs of large metacentrics in the 2 n  = 26 form. In this study, the karyotypes of the numerically extreme forms (2 n  = 26 and 2 n  = 36) have been illustrated and described in detail, and a new scheme of nomenclature is proposed for the chromosomal rearrangements observed in N. lapillus . Chromosome numbers and karyotypes were recorded and analysed from 70 sites throughout its wide geographical range, mainly from around the UK coasts but also from sites in Norway, France, Spain, Portugal and the USA, showing remarkable variation in both diploid number and karyotypic configuration. The results provide new evidence that seven chromosomes in the 2 n  = 26 form can be involved in the Robertsonian rearrangements, but the maximum recorded diploid number remains 2 n  = 36. Inversions were confirmed in three chromosomes and one population was found to exhibit aneuploidy. Possible explanations for the geographical trends in karyotypic variation are discussed, but despite the advances in the karyology of N. lapillus , a simple solution to this enigmatic phenomenon remains elusive.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 195–210.     

Karyological notes on eight species of Achillea L. (Asteraceae, Santolinoideae) from Turkey

The chromosome number and morphology of eight species belonging to the section Santolinoideae of the genus Achillea L. (Asteraceae) were investigated using karyological techniques. The species studied were Achillea cucullata (Hausskn.) Bornm., A. vermicularis Trin., A. monocephala Boiss. & Bal., A. boissieri (Hausskn.) Bornm., A. santolina L., A. gypsicola Hub.-Mor., A. goniocephala Boiss. & Bal., and A. spinulifolia Fenzl ex Boiss. In these species, the chromosome numbers were 2 n  = 18 in A. vermicularis , A. monocephala , and A. boissieri , 2 n  = 18A + 1B in A. spinulifolia , 2 n  = 36 in A. cucullata and A. santolina , and 2 n  = 54 in A. gypsicola and A. goniocephala . All of the chromosomes had median point (M), median region (m), or submedian (sm) centromeres. An increase in asymmetry was not observed in the karyotypes of the species.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 573–580.     

Phylogenetic relationships of Atherina hepsetus and Atherina boyeri (Pisces: Atherinidae) populations from Greece, based on mtDNA sequences

The genetic divergence and the phylogenetic relationships of six Atherina boyeri (freshwater and marine origin) and five Atherina hepsetus populations from Greece were investigated using partial sequence analysis of 12s rRNA, 16s rRNA and control region mtDNA segments. Three different well divergent groups were revealed; the first one includes A. boyeri populations living in the sea, the second includes A. boyeri populations living in the lakes and lagoons whereas the third one includes all A. hepsetus populations. Fifty-seven different haplotypes were detected among the populations studied. In all three mtDNA segments examined, sequence analysis revealed the existence of fixed haplotypic differences discriminating A. boyeri populations inhabiting the lagoon and the lakes from both the coastal A. boyeri and the A. hepsetus populations. The genetic divergence values estimated between coastal (marine) A. boyeri populations and those living in the lagoon and the lakes are of the same order of magnitude as those observed among coastal A. boyeri and A. hepsetus populations. The results obtained by different phylogenetic methods were identical. The deep sequence divergence with the fixed different haplotypes observed suggests the occurrence of a cryptic or sibling species within A. boyeri complex.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 151–161.     

A new species of Arctotis (Compositae, Arctotideae) from kommetjie grassland in Eastern Cape Province, South Africa

Arctotis debensis R.J.McKenzie, a new species from the Albany Centre of Floristic Endemism, South Africa, is described and illustrated. It grows almost exclusively in grassland on kommetjies, a distinctive landform of depressions and mounds associated with giant earthworms, in a restricted area west of King William's Town, Eastern Cape Province. It is the first plant taxon reported to be endemic or near-endemic to this unusual habitat. The new species appears to have been collected rarely and previous collections examined have remained undetermined to species level. The new species is distinguished from closely allied species by the combination of its usually larger dimensions in all parts, prostrate habit, coriaceous leaves that are green, scabrous, and eglandular on the adaxial surface and densely lanate on the abaxial surface, and involucral-bract morphology.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 581–588.     

Chromosome study of the fern genus Cyrtomium (Dryopteridaceae)

Cyrtomium (Dryopteridaceae) is an Asiatic genus comprising about 40 species characterized by having anastomosing veins that form areolae with included veinlets. Twelve chromosome counts representing 11 taxa were made in the present study. The chromosome numbers of six species endemic to China are reported for the first time: C. uniseriale , 2 n  = 164; C. guizhouense , 2 n  = 82; C. shingianum , n  = 82, 2 n  =  c .164; C. chingianum , 2 n  = 164; C. urophyllum , 2 n  = 82 and C. aequibasis , 2 n  = 123. The results were used to show that (1) C. uniseriale should be reduced to varietal status under C. balansae ; (2) subseries Balansana is not closely related to any other Cyrtomium species and should be separated from Cyrtomium ; and (3) C. guizhouense and C. lonchitoides are basal groups when subseries Balansana is not considered. These results were also supported by morphology. A high level of differentiation is a distinct characteristic in Cyrtomium . The genus has two reproductive types: sexual and apogamous. Sexual species are distributed mostly in China. Southwestern China is a modern diversity centre of Cyrtomium , with 80.6% of known species occurring there. Many species are endemic, most of which are sexual tetraploids or apogamous triploids. Both the apogamous reproductive type and polyploid species are adaptions to limestone habitats.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 221–228.     

Intra-annual genetic variation in the downstream larval drift of sutchi catfish (Pangasianodon hypophthalmus) in the Mekong river

Larvae of the sutchi catfish Pangasianodon hypophthalmus were collected during peak downstream drift in the Lower Mekong river on four occasions over an 8-week period during the 2003 spawning season, and genotyped using seven microsatellite loci. We provide evidence for several heterogeneous groups within and among the temporally discrete larval peak samples. Strong evidence for a significant deficit of heterozygotes was observed for each larval sample and the pooled sample, possibly due to population admixture. Although individual-based assignment tests suggested that each larval peak sample was admixed, significant but low genetic differentiation was observed among larval samples ( F _ST = 0.0052, P  < 0.01). The lack of significant relatedness confirms the multifamily composition of each larval group, excluding family bias to explain the observed genetic heterogeneity. Both the entire larval peak and each temporally separated larval peak originated from spawning groups with heterogeneous allelic composition involving several distinct spawning events. We propose three explanations to account for our findings: (1) the ecological match/mismatch hypothesis; (2) the genetic 'sweepstakes' selection hypothesis; and (3) life-history-specific characteristics of the spawning populations. Finally, an intra-annual shift in the contribution of the spawning populations to the larval drift was detected on successive occasions.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 719–728.     

New chromosome counts in the genus Cousinia (Asteraceae) from Iran

Chromosome counts are reported of 38 populations representing 24 species of the genus Cousinia from Iran, one of the main centres of speciation of the genus. Sixteen of the counts are new to science. Our results confirm that Cousinia exhibits a complex dysploid series ranging from x  = 13 to x  = 9. One of the basic chromosome numbers, x  = 9, is new for the genus and must be confirmed. Some considerations on the correlation between chromosome numbers and section classification are made.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 411–419.     

New or rarely reported chromosome numbers in taxa of subtribe Artemisiinae (Anthemideae, Asteraceae) from Mongolia

This study encompasses 25 chromosome counts of 18 species in the subtribe Artemisiinae (tribe Anthemideae) of the family Asteraceae, from Mongolia. Most (15 species) belong to Artemisia , the largest genus of the subtribe, whereas the others come from two genera very closely related to it: Ajania (two species) and Neopallasia (one species). Eleven counts are new reports, three are not consistent with previous reports and the remainder confirm scanty earlier information. The majority of the species have x  = 9 as their basic chromosome number, but there are some taxa with x  = 8. Ploidy levels range from 2 x to 6 x . The presence of B-chromosomes was detected in Ajania fruticulosa .  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 203–210.     

Historical influences on genital morphology among sympatric species: gonopod evolution and reproductive isolation in the crayfish genus Orconectes (Cambaridae)

Freshwater crayfishes represent an incredibly diverse component of temperate aquatic ecosystems. The genus Orconectes (Cambaridae) comprises approximately 17% of total global crayfish diversity and is native to central and eastern North America. Using both Bayesian and parsimony-based phylogenetic hypotheses from complete cytochrome c oxidase subunit I (COI) mtDNA sequence data (1545 bp) along with information on male gonopod shape and species distribution patterns, we examined the evolution of male genital morphology and its potential influence on species co-occurrence. We found that sympatric species exhibited similar male genital morphology more often than expected based on the frequency of genital shapes within the genus. When evolutionary history was incorporated into this analysis, the result was no longer significant, suggesting that species co-occurrence and the associated genital shapes of sympatric congeners cannot be explained solely by interspecific ecological interactions. Our results also do not support the current subgeneric classifications within Orconectes or the monophyly of the genus, both of which have been based previously on male genital morphology.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 1–12.     

Chromosome numbers in Brazilian species of Crotalaria (Leguminosae, Papilionoideae) and their taxonomic significance

Chromosome numbers were counted for 23 species of Crotalaria native to Brazil. Among these data there were new counts for 15 taxa, and some confirmed previous reports or represented numbers that were different from those cited previously. The chromosome numbers most frequently found were 2 n  = 16 and 2 n  = 32. Only C. incana L. had 2 n  = 14 and C. tweediana Benth. had 2 n  = 54. The counts 2 n  = 32 and 54 were found in species of section Calycinae and 2 n  = 16 and 14 in species of section Chrysocalycinae . The data revealed the importance of chromosomal parameters in the characterization of sections Calycinae and Chrysocalycinae in Brazil. We discuss the systematic significance and evolutionary aspects for the genus, comparing the results with the two sections that are native in Brazil.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 271–277.     

Karyological studies in Tripleurospermum (Asteraceae, Anthemideae) from north-east Anatolia

Chromosome number and morphology in 14 taxa belonging to 19 populations of Tripleurospermum Sch. Bip. were studied using karyological and numerical taxonomical techniques. Data on chromosome measurements were analysed using cluster analysis. Chromosome numbers of these taxa are 2 n  = 2 x  = 18, 4 x  = 36 and 5 x  = 42–48. Seven records are new, two are not consistent with previous counts, and the remainder confirm the very limited previous data (one to three records). A new ploidy level (pentaploidy) is reported for the first time for the genus. Some correlations between ploidy levels and morphological characters are noted and several systematic and evolutionary aspects of the genus are discussed in the light of karyological data.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 146 , 427–438.     

Concerted evolution of 18–5.8–26S rDNA repeats in Nicotiana allotetraploids

We review and extend data showing concerted evolution of parental 18–5.8–26S nuclear ribosomal DNA (18–26S rDNA) gene families in three natural Nicotiana allotetraploids ( N. tabacum , N. rustica and N. arentsii , each 2 n  = 4 x  = 48) and one synthetic N. tabacum line (Th37, ♀ N. sylvestris (2 n  = 24) × ♂ N. tomentosiformis (2 n  = 24)). The origin of the gene families was analysed by sequence polymorphisms in the intergenic spacer (IGS) region and the number of chromosomal loci by fluorescence in situ hybridization (FISH). FISH revealed that the number and locations of 18–26S rDNA in the natural allopolyploids was the sum of those found in the diploid progenitors. However, the rDNA restriction patterns showed polymorphisms in the IGS that were not additive, suggesting that parental rDNA clusters were partially ( N. tabacum, N. rustica ) or completely ( N. arentsii ) overwritten by hybrid-specific units. Thus the Nicotiana allotetraploids show evidence of concerted evolution, including both intralocus and interlocus gene conversion. A feral N. tabacum collected in Bolivia had a higher proportion of unconverted parental rDNA units than cultivated tobacco varieties, suggesting either that rDNA homogenization is accelerated by inbreeding or multiple origins of tobacco. There is no evidence for the elimination of N. sylvestris- derived rDNA units in the synthetic Th37 tobacco line as occurred in natural tobacco, although several novel rDNA unit variants were found in most but not all the hybrid plants. Factors that may control the occurrence and extent of rDNA homogenization are discussed for allopolyploids in Nicotiana and other taxa.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 615–625.