scholarly journals Microevolutionary change in viscerocranial bones under congeneric sympatry in the Lake Tanganyikan cichlid genus Tropheus

Hydrobiologia ◽  
2021 ◽  
Author(s):  
Michaela Kerschbaumer ◽  
Lisbeth Postl ◽  
Christian Sturmbauer
Keyword(s):  
Trophic Niche ◽  
Living Alone ◽  
Niche Separation ◽  
Rocky Shores ◽  
Shape Variation ◽  
Sympatric Populations ◽  
Eye Size ◽  
Microevolutionary Change ◽  
One Step ◽  
Morphological Differences

AbstractThe endemic Lake Tanganyika cichlid genus Tropheus lives at rocky shores all around the lake and comprises six species which are subdivided into about 120 morphologically similar but color-wise distinct populations. Typically, they live without a second Tropheus species, but there are some regions where two or even three sister species live in sympatry. We previously showed that there are morphological differences concerning head shape, eye size and insertion of fins among populations living alone compared to those living in sympatry with a second Tropheus. This study goes one step further to test if sympatry affects the shape of viscerocranial bones. By means of geometric morphometrics, we compare the shape of four bones among thirteen Tropheus populations, some of which in sympatry and some living alone. We quantify patterns of shape variation and estimate morphological disparity among the four bony elements in the study species and populations. We found consistent differences in the shape of one bony element among non-sympatric and sympatric populations, besides an extensive variation in the shape of viscerocranial bones within and among species. Furthermore, sexual dimorphism in Tropheus is clearly evident in the viscerocranial bones analyzed. We suggest that the relatively subtle morphological signal in sympatric vs. non-sympatric Tropheus populations is owed to the fact that the depth segregation does not yet represent a full shift in the trophic niche, albeit our data confirm that differences in ecologically relevant traits, such as bones of the preorbital region, play an important role in the process of niche separation and in the context of explosive diversification of cichlid fishes.

An exposure scale for marine shores in western Norway

1978 ◽  
Vol 58 (4) ◽  
pp. 975-996 ◽  
Author(s):  
D. H. Dalby ◽  
E. B. Cowell ◽  
W. J. Syratt ◽  
J. H. Crothers
Keyword(s):  
Species Abundance ◽  
Shell Shape ◽  
Rocky Shores ◽  
Shape Variation ◽  
Nucella Lapillus ◽  
Extended Form ◽  
Independent Evidence ◽  
The North ◽  
Western Norway ◽  
The North Sea

A rocky shore exposure scale, intended primarily for use in the Fensfjord area, Western Norway, has been prepared. This scale is developed from an earlier scale devised by Ballantine for Milford Haven, Wales, making use of species abundance curves along the wave exposure gradient. Independent evidence for the validity of the scale is provided by shell shape variation in Nucella lapillus and by the height of the black lichen zone in the supralittoral fringe. The successive steps in the preparation of the scale are outlined, definitions of the exposure grades are given in tabular form for the restricted set of species analysed numerically and descriptions are provided in an extended form to provide a fuller picture for users of the scale. It is believed that the scale will prove applicable to other rocky shores around the North Sea.

scholarly journals The impact of allometry on vomer shape and its implications for the taxonomy and cranial kinesis of crown-group birds

2020 ◽  
Author(s):  
Olivia Plateau ◽  
Christian Foth
Keyword(s):  
Anterior Part ◽  
Correct Identification ◽  
Temporal Region ◽  
Shape Variation ◽  
Crown Group ◽  
Multivariate Statistical ◽  
Morphological Differences ◽  
Cranial Kinesis ◽  
The Impact ◽  
Shape Data

AbstractCrown birds are subdivided into two main groups, Palaeognathae and Neognathae, that can be distinguished, among others, by the organization of the bones in their pterygoid-palatine complex (PPC). Shape variation to the vomer, which is the most anterior part of the PPC, was recently analysed by Hu et al. (2019) with help of geometric morphometrics to discover morphological differences between palaeognath and neognath birds. Based on this study, the vomer was identified as sufficient to distinguish the two main groups (and even more inclusive neognath groups) and their cranial kinetic system. As there are notable size differences between the skulls of palaeognaths and neognaths, we here investigate the impact of allometry on vomeral shape and its implication for taxonomic classification by re-analysing the data of the previous study. Different types of multivariate statistical analyses reveal that taxonomic identification based on vomeral shape is strongly impaired by allometry, as the error of correct identification is high when shape data is corrected for size. This finding is evident by a great overlap between palaeognath and neognath subclades in morphospace. The correct identification is further influenced by the convergent presence of a flattened vomeral morphotype in multiple neognath subclades. As the evolution of cranial kinesis has been linked to vomeral shape in the original study, the existing correlation between shape and size of the vomer across different bird groups found in the present study questions this conclusion. In fact, cranial kinesis in crown birds results from the loss of the jugal-postorbital bar in the temporal region and ectopterygoid in the PPC and the combination of a mobilized quadrate-zygomatic arch complex and a flexible PPC. Therefore, we can conclude that the vomer itself is not a suitable proxy for exploring the evolution of cranial kinesis in crown birds and their ancestors.

scholarly journals Characterization of the genetic architecture underlying eye size variation within Drosophila melanogaster and Drosophila simulans

2019 ◽  
Author(s):  
Pedro Gaspar ◽  
Saad Arif ◽  
Lauren Sumner-Rooney ◽  
Maike Kittelmann ◽  
Andrew J. Bodey ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Variation ◽  
Size Variation ◽  
Eye Size ◽  
Specific Variation ◽  
Gene Regulatory ◽  
Morphological Differences ◽  
Genomic Regions ◽  
Insect Eye

AbstractThe compound eyes of insects exhibit striking variation in size, reflecting adaptation to different lifestyles and habitats. However, the genetic and developmental bases of variation in insect eye size is poorly understood, which limits our understanding of how these important morphological differences evolve. To address this, we further explored natural variation in eye size within and between four species of the Drosophila melanogaster species subgroup. We found extensive variation in eye size among these species, and flies with larger eyes generally had a shorter inter-ocular distance and vice versa. We then carried out quantitative trait loci (QTL) mapping of intra-specific variation in eye size and inter-ocular distance in both D. melanogaster and D. simulans. This revealed that different genomic regions underlie variation in eye size and inter-ocular distance in both species, which we corroborated by introgression mapping in D. simulans. This suggests that although there is a trade-off between eye size and inter-ocular distance, variation in these two traits is likely to be caused by different genes and so can be genetically decoupled. Finally, although we detected QTL for intra-specific variation in eye size at similar positions in D. melanogaster and D. simulans, we observed differences in eye fate commitment between strains of these two species. This indicates that different developmental mechanisms and therefore, most likely, different genes contribute to eye size variation in these species. Taken together with the results of previous studies, our findings suggest that the gene regulatory network that specifies eye size has evolved at multiple genetic nodes to give rise to natural variation in this trait within and among species.

scholarly journals Morphological Differences and Trophic Niche Breadth of Sarotherodon galilaeus and Oreochromis niloticus from the Freshwater Lake Geriyo, North-Eastern Nigeria

2019 ◽  
Vol 77 (1) ◽  
pp. 19-32
Author(s):  
Azubuike Victor Chukwuka ◽  
Adedeji Hameed Adebowale ◽  
Oloyede Adeyemi Adekolurejo
Keyword(s):  
Oreochromis Niloticus ◽  
Niche Breadth ◽  
Stomach Contents ◽  
Trophic Niche ◽  
Spine Length ◽  
Dietary Preferences ◽  
Fin Ray ◽  
Limited Food ◽  
Sarotherodon Galilaeus ◽  
Morphological Differences

Abstract The relationship between morphological traits and feeding ecology of the only two tilapiine cichlids (Sarotherodon galilaeus and Oreochromis niloticus) in Lake Geriyo, northeastern Nigeria, was examined. Stomach contents of 504 individuals were examined and analyzed to relate morphological differences of each species to its dietary preferences. Eleven ecological relevant morphological variables, including total length, standard length, head length, body depth, eye diameter, pectoral spine length, pelvic spine length, dorsal fin ray count, dorsal spine count and anal fin ray count, were also measured and subjected to Principal coordinate analysis (PCoA) to relate morphological differences of each species to its dietary preferences. The PCoA (using Euclidean distance) revealed a large morphological distance between species indicating adaptation for different spatial and vertical distributions within the lake. Furthermore, the correlation of these morphological differences with particular diet categories suggests a potential for specialized trophic tendencies, however, the high occurrence of two major food types (macrophytes and plankton) in stomach contents of both species indicate generalist trophic tendencies. While a high trophic overlap index (0.98) was recorded for both species, the trophic niche breadth was higher for S. galilaeus (4.18±0.32), compared to O. niloticus (3.33±0.24). Despite the large morphological differences of both tilapias, the high trophic overlaps indicate limited food options within Lake Geriyo. In addition, the successful coexistence of the tilapias in the face of limited food resources indicates suitable partitioning of food resources in the lake.

scholarly journals Description of two new species of the genus Cacopsylla Ossiannilsson, 1970 (Hemiptera, Psylloidea) from northern Fennoscandia recognized by morphology, cytogenetic characters and COI barcode sequence

2019 ◽  
Vol 13 (4) ◽  
pp. 367-382 ◽  
Author(s):  
Christina Nokkala ◽  
Valentina G. Kuznetsova ◽  
Veikko Rinne ◽  
Seppo Nokkala
Keyword(s):  
Tree Line ◽  
Nucleotide Substitutions ◽  
Sympatric Populations ◽  
Bisexual Species ◽  
Vaccinium Uliginosum ◽  
Parthenogenetic Species ◽  
Ledum Palustre ◽  
Northern Fennoscandia ◽  
Morphological Differences ◽  
Female Genital

Based on chromosomal, molecular and morphological analyses, two new Cacopsylla Ossiannilsson, 1970 species are described, C. lapponica S. Nokkala & Ch. Nokkala, sp. nov. and C. borealis S. Nokkala et Ch. Nokkala, sp. nov. (Hemiptera, Psylloidea). C. lapponica is a rare bisexual alpine species living on Vaccinium uliginosum Linnaeus, 1753 above tree line on northern hills, where it forms sympatric populations with C. myrtilli W. Wagner, 1947. So far, the species has been found in northern Finland, Utsjoki and Kilpisjärvi, and in northern Sweden, Abisko. The chromosome number in males is 2n = 12+X(0), characteristic of psyllids. The species is easily distinguished from C. myrtilli by its conspicuously smaller size mainly due to difference in wing size. Additional morphological differences are found in the length of antennae, female genital plates and male parameres. C. borealis, in turn, is a relatively common apomictic parthenogenetic species with 5n = 60 + XXXXX living on the same host plant, Ledum palustre Linnaeus, 1753, as C. ledi (Flor, 1861) and occasionally forming sympatric populations with it. No males have been recorded in C. borealis. Its distribution range reaches at least from northern Fennoscandia to Lake Baikal in the East. C. borealis can be distinguished from C. ledi by differences in the length and width of antennae, dark brown markings on the wing and female terminal structures. For molecular analysis, a 638 bp fragment of the mitochondrial COI gene was sequenced. C. lapponica differs from the cohabitating C. myrtilli by 20 fixed nucleotide substitutions (uncor rected p-distance 3.13 %), while C. borealis differs from C. ledi by 21 fixed nucleotide substitutions (uncorrected p-distance 3.29 %). Molecular phylogeny construction (ML and BI) reveals two highly divergent clades, one comprising two bisexual species, C. lapponica and C. fraudatrix Labina & Kuznetsova, 2012, and the other clade comprising the parthenogenetic species C. borealis, C. myrtilli, and C. ledi. Within this clade, C. borealis is more closely associated with C. myrtilli than with C. ledi.

Microhabitat Segregation of the Threatened Spotted Darter (Etheostoma maculatum) and Closely Related Orangefin Darter (E. bellum)

1993 ◽  
Vol 50 (5) ◽  
pp. 1084-1091 ◽  
Author(s):  
Richard K. Kessler ◽  
James H. Thorp
Keyword(s):  
Threatened Species ◽  
Narrow Range ◽  
Microhabitat Use ◽  
Sympatric Populations ◽  
High Discharge ◽  
Substrate Use ◽  
Quantitative Sampling ◽  
Morphological Differences ◽  
Species Specific ◽  
Microhabitat Segregation

We examined differences in microhabitat use in sympatric populations of the closely related spotted darter (Etheostoma maculatum) and orangefin darter (E. bellum) (subgenus Nothonotus). Sample plots and underwater observations were employed to assess patterns of microhabitat use by both species. Quantitative sampling using a prepositioned electrofishing sampler demonstrated that species segregated by microhabitats. Etheostoma maculatum occupied areas of greater depth and larger, more diverse substrate sizes than E. bellum in July and October of 1991. Underwater observations also revealed species-specific differences in substrate use. Etheostoma maculatum was observed mostly under rocks whereas E. bellum was more general in substrate use. The narrow range of microhabitat use by E. maculatum may contribute to its status as a threatened species in Kentucky. During July 1991, an unusually high discharge month that year, males of both species occupied microhabitats of significantly higher velocities and larger substrate sizes than females. Our data suggest that opportunities for coexistence between these closely related darters are enhanced by microhabitat partitioning which is linked to behavioral and morphological differences.

Lack of morphological differentiation in eastern (Rhinichthys atratulus) and western (Rhinichthys obtusus) blacknose dace in Canada

2005 ◽  
Vol 83 (11) ◽  
pp. 1502-1509 ◽  
Author(s):  
B A Fraser ◽  
N E Mandrak ◽  
R L McLaughlin
Keyword(s):  
Multivariate Analyses ◽  
Morphological Differentiation ◽  
Morphological Characters ◽  
Sympatric Populations ◽  
Diagnostic Characters ◽  
Allopatric Populations ◽  
Rhinichthys Atratulus ◽  
Blacknose Dace ◽  
Morphological Differences ◽  
Colouration Pattern

We tested whether eastern (Rhinichthys atratulus (Herman, 1804)) and western (Rhinichthys obtusus Agassiz, 1854) blacknose dace could be differentiated in Canada. Eastern, western, and southern forms of blacknose dace had been considered subspecies until recently, when separation of eastern and western species was accepted (J.S. Nelson et al. 2004. Am. Fish. Soc. Spec. Publ. No. 29). However, no study has examined morphological differences in purported diagnostic characters between the two species in Canada. Mensural, meristic, and colouration pattern characters purported to distinguish the two species were measured for blacknose dace across their Canadian range, including likely zones of sympatry. Univariate and multivariate analyses of morphological characters could not distinguish between individuals in allopatric populations from eastern and western regions. Variation among individuals within sympatric populations did not differ significantly from the variation among individuals within allopatric populations, providing no evidence of divergence of the species in sympatry. The delineation of eastern and western species using morphology is not supported by this study, given the lack of differentiation in key distinguishing characters within the Canadian range of the species.

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