Sympatric Habitat Research Articles

Buddleja caryopteridifolia (Scrophulariaceae), a species to be recognized based on morphology, floral scent and AFLP data

Buddleja caryopteridifolia was treated as a synonym of B. crispa in Flora of China. However, it was found that the two entities had different phenologies as well as morphology in the sympatric habitat investigated. Buddleja crispa flowers from mid-March to mid-May while B. caryopteridifolia blooms from early June to mid-September. In this study, the comprehensive comparative analyses of morphological traits, floral scent composition and amplified fragment length polymorphism (AFLP) data were utilized to determine whether B. caryopteridifolia should be recognized as a separate species. Among 13 morphological characters, all but calyx length were significantly different (all p<0.05, t-test) between the two species. Both cluster analysis and principal coordinates analysis (PCoA) of AFLP markers produced two distinct clusters for B. crispa and B. caryopteridifolia. The results of floral scent indicated several differences between B. crispa and B. caryopteridifolia. The main volatile compound of B. crispa was Benzaldehyde, while that of B. caryopteridifolia mostly consisted of trans-β-Ocimene. Therefore, all analyses supported the rehabilitation of B. caryopteridifolia as an independent species.

Mitochondrial capture misleads about ecological speciation in the Daphnia pulex complex.

The North American ecological species Daphnia pulicaria and Daphnia pulex are thought to have diverged from a common ancestor by adaptation to sympatric but ecologically distinct lake and pond habitats respectively. Based on mtDNA relationships, European D . pulicaria is considered a different species only distantly related to its North American counterpart, but both species share a lactate dehydrogenase (Ldh) allele F supposedly involved in lake adaptation in North America, and the same allele is also carried by the related Holarctic Daphnia tenebrosa . The correct inference of the species’ ancestral relationships is therefore critical for understanding the origin of their adaptive divergence. Our species tree inferred from unlinked nuclear loci for D . pulicaria and D . pulex resolved the European and North American D . pulicaria as sister clades, and we argue that the discordant mtDNA gene tree is best explained by capture of D . pulex mtDNA by D . pulicaria in North America. The Ldh gene tree shows that F-class alleles in D . pulicaria and D . tenebrosa are due to common descent (as opposed to introgression), with D . tenebrosa alleles paraphyletic with respect to D . pulicaria alleles. That D . tenebrosa still segregates the ancestral and derived amino acids at the two sites distinguishing the pond and lake alleles suggests that D . pulicaria inherited the derived states from the D . tenebrosa ancestry. Our results suggest that some adaptations restricting the gene flow between D . pulicaria and D . pulex might have evolved in response to selection in ancestral environments rather than in the species’ current sympatric habitats. The Arctic ( D . tenebrosa ) populations are likely to provide important clues about these issues.

New Report of the Varunid Crabs, Hemigrapsus takanoi and Sestrostoma toriumii (Crustacea: Decapoda: Varunidae) from Korea

As a result of continuous taxonomic studies on the Korean crabs, two varunid crabs, Hemigrapsus takanoi Asakura and Watanabe, 2005 and Sestrostoma toriumii (Takeda, 1974), are newly reported from Korean waters. Hemigrapsus takanoi, as a sibling species of H. penicillatus, has not been recognized in Korean waters, and this species occurs in the sympatric habitat with H. penicillatus in the Korean peninsula. Sestrostoma toriumii (Takeda, 1974) is associated with thallassinid Upogebia major (De Haan, 1841) and echiuran Urechis unicintus (Von Drache, 1881) as the case of S. balssi (Shen, 1932). The Korean S. toriumii showed smaller size than those mentioned in the original description. Their illustrations and pictures are provided with descriptions, and the distributions of these species in the Korean peninsula are also provided.

Chromosomal study of the lenoks, Brachymystax (Salmoniformes, Salmonidae) from the South of the Russian Far East

An investigation of the karyotypes of two species of the genus Brachymystax (B. lenok and B. tumensis) has been done for the Russia Primorye rivers running to the East Sea basin, and others belonging to Amur basin. Based on the analysis of two species chromosome characteristics, combined with original and literary data, four cytotypes have been described. One of these cytotypes (Cytotype I: 2n=90, NF=110-118) was the most common. This common cytotype belongs to B. tumensis from the rivers of the East Sea basin and B. lenok from the rivers of the Amur basin, i.e. extends to the zones of allopatry. In the rivers of the Amur river basin, in the zone of the sympatric habitat of two species, each taxon has karyotypes with different chromosome numbers, B. tumensis (2n=92) and B. lenok (2n=90). Because of the ability to determine a number of the chromosome arms for these two species, additional cytotype have been identified for B. tumensis: Cytotype II with 2n=92, NF=110-124 in the rivers basins of the Yellow sea and Amur river and for B. lenok three cytotypes: Cytotype I: 2n=90, NF=110 in the Amur river basin; Cytotype III with 2n=90, NF=106-126 in the Amur river basin and Cytotypes IV with 2n=92, NF=102 in the Baikal lake.

The integration of locomotion and prey capture in divergent cottid fishes: functional disparity despite morphological similarity

Many mobile animals rely on the integration of locomotion and feeding to capture prey. Fishes commonly swim up to a prey item and utilize a combination of ram and suction feeding for prey capture. Marine cottids represent a diverse and abundant lineage of fishes that exhibit variation in feeding mode that is related to their mouth morphology. However, little is known regarding the integration of the locomotor and feeding systems during prey capture. We quantified the feeding kinematics, feeding performance and integration of locomotion and feeding in two species of divergent cottids: Blepsias cirrhosus (silver-spotted sculpin) and Oligocottus maculosus (tidepool sculpin). Individuals were caught from sympatric habitats near the Bamfield Marine Sciences Centre on Vancouver Island and filmed with a high-speed video camera (500 Hz) while feeding on amphipod prey. Two principal component axes summarize differences in integration and feeding mode despite similarity in attack velocity and feeding morphology (peak gape, peak cranial elevation and peak jaw protrusion). A greater number of correlations between locomotor and feeding variables in B. cirrhosus, compared with O. maculosus, indicate greater integration. We conclude that traditional measures of attack kinematics do not capture functionally and ecologically relevant differences between species. The mechanisms underlying differences in locomotor strategy likely result from unexplored morphological or ecological differences between species. In cottids, integration is apparent in more basal, subtidal species such as B. cirrhosus, and the need for integration may be superceded by demands from the habitat in more derived, shallow-water species such as O. maculosus.

Migratory history of Rhinogobius sp. OR morphotype “Shimahire” as revealed by otolith Sr:Ca ratios

The migratory history of the Rhinogobius sp. OR morphotype “Shimahire” collected from a slower current environment in the Maruyama River, the Ibo River, and the Kako River, Japan, was studied by examining the strontium and calcium concentrations in the otoliths. The otolith Sr:Ca ratios of almost all samples showed consistently low ratios from the core to the edge, reflecting the fact that the organisms had been living in a freshwater environment their entire lives. The ratios of Rhinogobius sp. CB and Rhinogobius flumineus living in the sympatric habitats with the Rhinogobius sp. OR morphotype “Shimahire” in the Kako River showed an amphidromous and fluvial life cycle, respectively. These findings suggest that the Rhinogobius sp. OR morphotype “Shimahire” has a freshwater resident life cycle.

BEHAVIORAL INTERACTIONS BETWEEN COEXISTING SPECIES: SONG PLAYBACK EXPERIMENTS WITH WOOD WARBLERS

Behavioral interactions between coexisting species may reflect underlying ecological interactions or may arise from factors unrelated to ecological interactions between species. We examined behavioral interactions between two coexisting, migratory wood warblers that competitively interact on breeding territories in central Arizona, USA. The larger Orange-crowned Warbler (Vermivora celata) is aggressive toward the later-arriving Virginia's Warbler (V. virginiae) and responds to playback of Virginia's Warbler songs by approaching the playback speaker or by singing over Virginia's Warbler songs. Virginia's Warblers retreat from interactions with Orange-crowned Warblers and avoid the playback speaker when presented with Orange-crowned Warbler songs. Responses of both species to song playback of the opposite species differed from responses to conspecific songs, indicating that behavioral interactions do not result from misdirected intraspecific aggression. Behavioral responses were consistent with observed ecological interactions between the two species and suggest that asymmetrical behavioral aggression by the dominant Orange-crowned Warbler may be an important mechanism for competitive interactions involving nest sites. These results support previous studies that have used behavioral experiments to infer ecological interactions among coexisting species. While Orange-crowned Warblers may benefit from aggressively excluding Virginia's Warblers from preferred nest sites, limited data on Virginia's Warbler settlement patterns suggest that Virginia's Warblers do not avoid settling on Orange-crowned Warbler territories. Similar reproductive success in sympatric vs. allopatric habitats suggests little consequence for Virginia's Warblers settling with Orange-crowned Warblers, despite increased reproductive success of Virginia's Warblers in sympatric habitat when Orange-crowned Warblers were experimentally removed.

Multiple areas of acute vision in two freshwater teleosts, the creek chub, Semotilus atromaculatus (Mitchill) and the cutlips minnow, Exoglossum maxillingua (Lesueur)

The topography of Nissl-stained cells within the retinal ganglion cell layer is examined in two closely related freshwater teleosts from the family Cyprinidae. Regardless of the close phylogenetic relationship and the sympatric habitats of the two species, pronounced differences in the number and position of areas of increased cell density are observed in their retinae. in the creek chub, Semotilus atromaculatus, a midwater crepuscular feeder, three retinal specializations or areae centrales are identified in the dorsonasal, nasal, and temporal regions of the retina. In the cutlips minnow, Exoglossum maxillingua, a benthic diurnal feeder, two areae centrales are identified in temporal and nasal retina. The upper limits of the spatial resolving power of each species are calculated from the spacing of cells within the ganglion cell layer. Differences in the arrangement of isodensity contours appear to reflect the symmetry of each species' visual environment. The development and significance of up to three visually acute zones are discussed.

Comparative studies on the population dynamics ofMazus japonicus andM. Miquelii, scrophulariaceae

The population dynamics ofMazus japonicus andM. Miquelii was compared. In contrast with the summer annual growth habit (Vandellia crustacea) and the winter one(Veronica persica), M. japonicus had a “year-long annual growth habit” as the population of this species existed all year-round, notwithstanding that each individual of the population germinated and died within a year. TwoMazus species were sympatric on the levee of a rice paddy field where many other species were thickly grown. Those two species were difficult to propagate there, because their seeds, which were light germinators, could hardly germinate in the shade of other plants, or even if germination was possible, their seedlings may have soon died. However, asM. Miquelii, a perennial species, was able to reproduce by stolon vegetatively, it was a dominant species on the levee. On the contrary, the population density ofM. japonicus was thicker in the abandoned paddy field and an upland field than that ofM. Miquelii, because seeds of the former germinated under a greater variety of temperatures and under conditions of less soil moisture than those of the latter. These observations present an example of the fact that the difference of the reproductive strategy in annual and perennial plants has a striking effect on the population dynamics in the sympatric habitat.