Population structure of mud flounder Paralichthys orbignyanus from the south-western Atlantic Ocean

The mud flounder Paralichthys orbignyanus (Pleuronectiformes, Paralichthyidae) inhabits shallow waters of low salinities and mud bottoms in the temperate marine coastal regions of the Bonaerensean Ecoregion of the Argentinean Biogeographic Province in the south-western Atlantic Ocean. Specimens of P. orbignyanus were collected from Lagoa dos Patos (LDP) (southern Brazil), Mar Chiquita (MCH) and Marisol (MAR) both located in Buenos Aires (Argentina), and San Antonio Oeste (SAO) in the San Matías Gulf, Rio Negro (Argentina). A fragment of the mitochondrial DNA of the Control Region and seven microsatellite loci were characterized. In the Control Region, P. orbignyanus showed high variability, low nucleotide diversity, mild population expansion and a coalescence time of 35,000 years before the present. Flounders provided evidence of a genetic structure between the sampling sites LDP, MCH, MAR vs. SAO. On the other hand, P. orbignyanus displayed a lower to moderate contemporary genetic structure among all samples except between LDP and MCH. With no evidence of isolation by distance, this analysis supports a model of limited gene flow that is likely to be associated with a consistent larvae retention in all sampling sites. In addition, the present connectivity is ascribed to a lower migration process from SAO in the San Matías Gulf congruent with the prevailing littoral drift.     

First Record of Undaria Pinnatifida (Laminariales, Phaeophyta) in Southern Patagonia, Argentina

The Japanese kelp Undaria pinnatifida was found on 7th September 2005 in Ría Deseado (Santa Cruz, Argentina). This invasive algae was registered from the lower intertidal to the upper levels of the subtidal zone. The sporophytes were fixed to slabs, gravel and rocks of variable sizes and were also present as epibionts of tunicates. The sporophytes total length ranged between 3 and 88 cm, with a mean of 28.75 cm in the intertidal and 38.3 cm in the subtidal. The density and biomass increased from the intertidal to the subtidal. The kelp population showed a higher number of small immature individuals in the intertidal than␣subtidal where the organisms were bigger and with more individual biomass. This first record of U. pinnatifida in Southern Patagonia extends its southern distribution limit in Argentina, showing progressive expansion in the southwestern Atlantic. More surveys must be conducted to understand the evolution of U. pinnatifida invasion and its impact on the native benthic community.     

Parasites as biological tags for stock discrimination of the Brazilian flathead Percophis brasiliensis in the south-west Atlantic

Three stocks of the Brazilian flathead Percophis brasiliensis were identified on the coast of Argentina and Uruguay using parasites as biological tags. A total of 177 fish were examined and 23 parasite species were found. Fish were caught in four zones: north of the Argentine–Uruguayan Common Fishing Zone (34°30′–36°30′ S; 53°30′–56°00′ W), south of the Argentine–Uruguayan Common Fishing Zone (38°08′ S 57°32′ W), El Rincón zone (39–41° S; 60–62° W) and San Matías Gulf (41°40′–42°10′ S; 63°50′–65°00′ W). Discriminant analyses allowed the identification of three discrete stocks in the four zones (86·44% of classified samples were correctly identified), with P. brasiliensis from both north and south of the Argentine–Uruguayan Common Fishing Zone clumping together, as a single stock. Some species were important in discriminating among groups, Anisakis simplex was related to southern areas, while Grillotia sp., Corynosoma australe and Hysterothylacium sp. were important in determining the position of fish from the Argentine–Uruguayan Common Fishing Zone. These results were corroborated by comparing parasite prevalence and abundance among zones. The main differences were observed in those comparisons involving fish from the San Matías Gulf. Fish from the Argentine–Uruguayan Common Fishing Zone were characterized by higher infections of Grillotia sp., C. australe, Corynosoma cetaceum and Hysterothylacium sp., while the samples from El Rincón and San Matías Gulf showed higher infections of A. simplex. Samples from San Matías Gulf were characterized by lower levels of parasitism for all other species. Differences in environmental factors and their influence on the distribution of zooplankton and other hosts in the food web may be differentially shaping the parasite community structure in each zone, resulting in identifiable stocks of the P. brasiliensis. The present study confirmed the existence of regional biological tags that delineated fish assemblages.     

The expanding range of Undaria pinnatifida in southern New Zealand: distribution, dispersal mechanisms and the invasion of wave-exposed environments

Very few studies have addressed how the invasive kelp Undaria pinnatifida (Harvey) Suringar spreads beyond initial founding populations in harbours. Surveys of the harbours and accessible areas of open coast throughout southern New Zealand were conducted to determine how far U. pinnatifida populations had extended since initial incursions. Our findings clearly demonstrate that U. pinnatifida is capable of invading native communities and can establish reproductive populations in locations subjected to significant and consistent wave action. The extent of spread from source populations differs between harbours in which it has established. Dispersal is greatest in harbours with long established populations, those where populations have not been strategically managed, harbours with high water exchange with surrounding coastal waters, and where prevailing currents allow establishment of U. pinnatifida on suitable substrata close to harbour entrances. Dispersal along the open coast is primarily achieved by drifting adult sporophytes that are washed up in the rocky intertidal zone. Founding populations are most often found in the intertidal zone, primarily within rockpools. Subtidal transects and observations indicate that U. pinnatifida is well adapted to invade exposed coastlines and can establish within a broad range of niches in wave-exposed areas including rockpools, the low intertidal, shallow subtidal, Macrocystis pyrifera kelp forests, and in low light areas beyond the vertical extent of large native macroalgae. The current range of U. pinnatifida is much greater than expected and appears to be expanding. Due to its ability to grow in a broad range of environments and to form dense monospecific stands, U. pinnatifida has the potential to strongly modify almost all rocky subtidal and intertidal communities in temperate locations.     

Reproductive traits of the small Patagonian octopus Octopus tehuelchus

This study evaluated the reproductive features of Octopus tehuelchus in three coastal environments of San Matías Gulf (Patagonia). Monthly samples of O. tehuelchus were used to estimate size at maturity, compare seasonal changes in oocyte size frequency distributions between sites as well as oocyte number and size between female maturity stage and sites. Females in Islote Lobos had a smaller size at maturity than females in San Antonio Bay and El Fuerte, probably as a consequence of a generally smaller body size. Males in San Antonio Bay were smaller at maturity than females. O. tehuelchus is a simultaneous terminal spawner. Fecundity (expressed as number of vitellogenic oocytes in ovary) was lower in Islote Lobos, and an increase in oocyte number in relation to female total weight was found. Females in San Antonio Bay had the largest oocytes, which may indicate higher energy reserves for the embryo and therefore higher juvenile survival. There was a close relationship between reproduction, growth and condition, represented as size at maturity, number and size of vitellogenic oocytes and period of maturity and spawning. Given the local variation in some reproductive features of O. tehuelchus, studies should focus on the environmental factors, which bring about this variation, and on how it affects the dynamics of local populations.     

INTRASPECIFIC VARIATION IN STRESS‐INDUCED HYDROGEN PEROXIDE SCAVENGING BY THE ULVOID MACROALGA ULVA LACTUCA1

We investigated the presence and kinetics of the oxidative stress response in intertidal and subtidal individuals of the ulvoid macroalga Ulva lactuca L. Stress responses, as measured with both enzymatic and fluorescent‐based antioxidant assays, differed between individuals collected from a subtidal and an intertidal habitat. Subtidal individuals secreted significantly more hydrogen peroxide (H₂O₂) than intertidal individuals when subjected to osmotic stress or desiccation. The activity of reactive‐oxygen‐scavenging enzymes and the ability to scavenge exogenous H₂O₂ were lower in subtidal than in intertidal individuals, suggesting that subtidal individuals are less stress tolerant. In vitro experimentation demonstrated that millimolar concentrations of dimethylsulfoniopropionate (DMSP) and its breakdown products could efficiently scavenge H₂O₂, with DMSP being a less‐effective scavenger than dimethyl sulfide (DMS), acrylic acid, and acrylate. The addition of H₂O₂ at concentrations of 2.5 mM or greater induced the cleavage of DMSP into DMS and acrylic acid in subtidal individuals. Intertidal individuals were affected in the same manner with the addition of 5 mM H₂O₂. There were no differences in the amounts of DMSP cleavage in subtidal and intertidal algae when the algae were subjected to hyposaline conditions. Our data suggest that the oxidative‐stress‐induced cleavage of DMSP affords products with efficient H₂O₂‐scavenging abilities. In addition, U. lactuca individuals growing in intertidal habitats are better acclimatized to changing environments and thus have a higher threshold for oxidative stress than conspecifics in subtidal habitats.     

Undaria mitochondrial large subunit ribosomal DNA (Phaeophyceae, Alariaceae): Structural properties and use for phylogenetic analysis

We sequenced mitochondrial 23S ribosomal DNA (rDNA) from two Undaria species and compared them with homologous sequences from related brown algae. The 23S rDNA sequences from Undaria pinnatifida (Harvey) Suringar were 2707 bp in length, of which 1290–1292 sites were assigned to stem regions and the rest to loop regions in the rRNA secondary structure model. In Undaria undarioides (Yendo) Okamura, the sequences were 2708–2709 bp in length and 1290 sites were assigned to stems. There were three sequence types among the seven U. pinnatifida individuals examined and two among the four U. undarioides individuals. A maximum parsimony analysis of these sequence data with those from related brown algal species resolved a robust monphyly of each of the two Undaria species, suggesting the utilities of 23S rDNA for phylogeny at species or intraspecific level in brown algae. Accounting for variations among sequences parsimoniously, sequence changes were sorted into 423 events, of which 165 were mapped to stems of the secondary structure.     

Seasonal growth,erosion rates,and nitrogen and photosynthetic ecophysiology of Undaria pinnatifida (Heterokontophyta) in southern New Zealand1

The goal of this study was to examine growth, erosion rates, and the photosynthetic and nitrogen ecophysiology of the invasive seaweed Undaria pinnatifida (Harv.) Suringar. Sporophytes of U. pinnatifida that appeared in Otago Harbour, southeastern New Zealand, in late autumn (May) 1996 were tagged, and their growth rates followed until the onset of senescence in early summer (November 1996). Blade growth rates were maximal between May and August when they ranged from 0.77 ± 0.05 to 0.93 ± 0.05 cm · d^?1 and declined from September onward. In laboratory experiments, U. pinnatifida took up nitrate and ammonium simultaneously at rates ranging from 21.3 ± 2.1 to 179.3 ± 65.1 μmol · g^?1 dry weight (dwt) · h^?1. When monthly patterns of growth rate, seawater inorganic nitrogen, nitrogen uptake kinetics, soluble tissue nitrate, % tissue carbon (C) and nitrogen (N), and C:N ratio were considered together, there was no evidence that N limited the growth of U. pinnatifida. Furthermore, the photosynthetic parameters P_max, α, E_k, E_c, and R_d derived from P versus E curves indicated that the growth of U. pinnatifida was not light limited, and that the population could potentially grow deeper than its observed location at 4 m depth. Nitrogen and light ecophysiological parameters of U. pinnatifida more closely resemble those of small, ephemeral seaweeds, such as Ulva, than other members of the Laminariales. We suggest that a “plastic” physiology may allow U. pinnatifida sporophytes to match their physiology to a range of environments, which is one reason for its success as an invasive seaweed.     

Nitrate uptake varies with tide height and nutrient availability in the intertidal seaweed Fucus vesiculosus

Intertidal seaweeds must cope with a suite of stressors imposed by aerial exposure at low tide, including nutrient limitation due to emersion. Seaweeds can access nutrients only when submerged, so individuals living higher compared to lower on the shore may have adaptations allowing them to acquire sufficient amounts of nutrients to survive and maintain growth. Using a combination of observations and experiments, we aimed to identify intraspecific variation in nitrate uptake rates across the intertidal distribution of F. vesiculosus, as well as test for acclimation in response to a change in tide height. We replicated our study at sites spanning nearly the entire Gulf of Maine coastline, to examine how local environmental variability may alter intraspecific variation in nitrate uptake. We found that average nitrate uptake rates were ~18% higher in upper compared to lower intertidal Fucus vesiculosus. Furthermore, we found evidence for both acclimation and adaptation to tide height during a transplant experiment. F. vesiculosus transplanted from the lower to the upper intertidal zone was characterized by increased nitrate uptake, but individuals transplanted from the upper to the lower intertidal zone retained high uptake rates. Our observations differed among Gulf of Maine regions and among time points of our study. Importantly, these differences may reflect associations between nitrate uptake rates and abiotic environmental conditions and seaweed nutrient status. Our study highlights the importance of long‐term variation in ambient nutrient supply in driving intraspecific variation of seaweeds across the intertidal gradient and local and seasonal variation in ambient nutrient levels in mediating intraspecific differences.     

Occurrence of the haemocyte parasite Bonamia sp. in flat oysters Ostrea puelchana farmed in San Antonio Bay (Argentina)

Culture of native flat oysters Ostrea puelchana d'Orbigny in San Antonio Bay (San Matías Gulf, Argentina) began in 1995. After elevated mortality (33%) occurred in September 1996, 18 mo after immersion, histopathological analysis and evaluation of parasitic prevalence was carried out. In October 1997, after 31 mo of cultivation, cumulative mortality was 80%, and in December of the same year, when individuals reached marketable size, mortality was 95% and culture was discontinued. The present study describes the haemocytic parasitism that affected O. puelchana, and suggests that a Bonamia sp. was the etiological agent. This parasite should be considered as a different species from Bonamia sp. detected in Australia and New Zealand until more studies are made to determine the correct taxonomy. This work constitutes the first record of this haemocyte parasite in flat oysters from the Argentinean coast.     

Slow zeaxanthin accumulation and the enhancement of CP26 collectively contribute to an atypical non-photochemical quenching in macroalga Ulva prolifera under high light

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants, which dissipates excess energy and further protects the photosynthetic apparatus under high light stress. NPQ can be dissected into a number of components: qE, qZ, and qI. In general, NPQ is catalyzed by two independent mechanisms, with the faster-activated quenching catalyzed by the monomeric light-harvesting complex (LHCII) proteins and the slowly activated quenching catalyzed by LHCII trimers, both processes depending on zeaxanthin but to different extent. Here, we studied the NPQ of the intertidal green macroalga, Ulva prolifera, and found that the NPQ of U. prolifera lack the faster-activated quenching, and showed much greater sensitivity to dithiothreitol (DTT) than to dicyclohexylcarbodiimide (DCCD). Further results suggested that the monomeric LHC proteins in U. prolifera included only CP29 and CP26, but lacked CP24, unlike Arabidopsis thaliana and the moss Physcomitrella patens. Moreover, the expression levels of CP26 increased significantly following exposure to high light, but the concentrations of the two important photoprotective proteins (PsbS and light-harvesting complex stress-related [LhcSR]) did not change upon the same conditions. Analysis of the xanthophyll cycle pigments showed that, upon exposure to high light, zeaxanthin synthesis in U. prolifera was gradual and much slower than that in P. patens, and could effectively be inhibited by DTT. Based on these results, we speculate the enhancement of CP26 and slow zeaxanthin accumulation provide an atypical NPQ, making this green macroalga well adapted to the intertidal environments.     

Sulfated polysaccharides from brown seaweeds Saccharina japonica and Undaria pinnatifida: isolation, structural characteristics, and antitumor activity

During the last decade brown seaweeds attracted much attention as a source of polysaccharides, namely laminarans, alginic acids, and sulfated polysaccharides—fucoidans, with various structures and biological activities.In this study, sulfated polysaccharides were isolated from brown seaweeds Saccharina japonica (formerly named Laminaria) and Undaria pinnatifida and their antitumor activity was tested against human breast cancer T-47D and melanoma SK-MEL-28 cell lines.The sulfated polysaccharide form S. japonica was highly branched partially acetylated sulfated galactofucan, built up of (1→3)-α-l-fucose residues. The sulfated polysaccharide from U. pinnatifida was partially acetylated highly sulfated galactofucan consisting of (1→3)- or (1→3);(1→4)-α-l-fucose residues.Fucoidans from S. japonica and U. pinnatifida distinctly inhibited proliferation and colony formation in both breast cancer and melanoma cell lines in a dose-dependent manner. These results indicated that the use of sulfated polysaccharides from brown seaweeds S. japonica and U. pinnatifida might be a potential approach for cancer treatment.     

A new species of the interstitial genus <Emphasis Type="Italic">Neopetitia</Emphasis> (Polychaeta,Syllidae, Eusyllinae) from Tenerife,with modified acicular chaetae in males

A new species of Neopetitia San Martín, 2003 is described from intertidal and shallow subtidal soft-bottom stations on the eastern and western coast of Tenerife, Canary Islands. The new species is characterized by the presence in males of a modified acicular chaeta in chaetiger 11. A discussion of known species of the genus is presented.     

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A new heteronemertean is described, Gastropionsanmatiensis n. gen. et n. sp. from Caleta de LosLoros, San Matías Gulf, Argentine Republic(41&; deg;S; 64° 05′ W). G. sanmatiensis is mainly defined by: (1) the structure ofits proboscis sheath; (2) enteronephridia and exonephridiasituated in the anterior part of the oesophagus; (3) a sphincterbetween the oesophagus and the intestine; (4) anintestinal sphincter. This lineid heteronemerteanseems to be very well adapted to oesophagealrespiration and excretion.     

Mutant induction in gametophytes of Undaria pinnatifida (Phaeophyceae) by heavy ion beam irradiation

Undaria pinnatifida, the brown macroalga, is a major commercial edible seaweed, and there is increasing interest in breeding new, improved cultivars for market expansion. In this study, we attempted to establish mutagenesis in U. pinnatifida using Ar and C ion beams as mutagens to meet future demands. To screen irradiated generations for mutants, U. pinnatifida zoospores irradiated with Ar and C ion beams were cultivated in plastic Petri dishes. Some gametophytes derived from the irradiated zoospores showed growth arrest or cell death at the initial developmental stage. Although the growth inhibition and lethal effects were observed at high doses of each ion irradiation, the Ar ion irradiation had high biological effects on cell division and growth. The gametophytes that showed a reduction in cell elongation were designated as an inhibited cell elongation mutant. A comparison of the mutant induction frequencies revealed that the C ion beam showed a higher frequency than the Ar ion beam. The highest frequency was 0.83% at 12.5 Gy of the C ion beam. We determined the total number of sporophytes and embryos per female gametophyte after sporophyte induction. High‐dose irradiation with the Ar ion beam decreased the embryo and sporophyte formation, suggesting that the Ar ion beam also has exhibited high biological effects on the fertilization or embryogenesis processes or both. The developed heavy ion mutagenesis and mutant screening methods would be useful for mutation breeding and constructing specific mutant libraries in brown algae, and not only in U. pinnatifida.     

The introduced alga Undaria pinnatifida (Laminariales,Alariaceae) in the lagoon of Venice

Since its appearance in 1992 in the lagoon of Venice, the brown algae Undaria pinnatifida (kelp) has gradually expanded along the banks of canals both at Chioggia and Venice, becoming the dominant species in the local algal community chiefly from February to July. In Chioggia Island, where another brown seaweed (Sargassum muticum) is present since 1992, the spreading of Undaria reaches a plateau. In Venice Island, instead, the colonisation process is still in progress. During 1999, the kelp has colonised the main canals (e.g. The Grand Canal) and, subsequently, the small inner ones. In order to evaluate the dynamics of substrate re-colonisation by Undaria, two mechanical eradications were carried out during (March) and after the fertile period (July) of the algae. Such experimental manipulations provided evidence of the fast re-colonisation potential of the algae mainly attributable to its efficient reproductive system. Eradication made during the fertile period, in fact, permitted the kelp development during the following year, while re-colonisation has started 2 years later where eradication was performed after the reproductive period. A significant decrease in the surface covered by other species has been observed both in shallow (Ulva rigida, Enteromorpha spp., Antithamnion pectinatum, Chondracanthus acicularis) and deeper areas (Rhodymenia ardissonei) during the period of maximum development of U. pinnatifida. On the basis of the results of this study, the following conclusions can be drawn: (1) the alga U. pinnatifida is continuously expanding in lagoon environments of Venice; (2) in order to limit its spreading, mechanical eradications would be done on a large spatial scale and before the zoospores release; (3) there is suggestive evidence of competition between Undaria and the remaining indigenous algae.     

Changes in biomass and botanical composition of beach-cast seaweeds in a disturbed coastal area from Argentine Patagonia

Trends in wrack composition and biomass, and its relationship with the anthropogenic impact were studied along a coastal area in Nuevo Gulf (south Patagonia) in front of Puerto Madryn city. Beach-cast macroalgae composition was sampled from 1992 to 1999 in the Puerto Madryn beaches and in several other nearby beaches in 1993, 1996 and 1998. Historical information was based on local knowledge and observations reported by marine biologists who worked in the area. The botanical composition of the beach-cast macroalgae in Puerto Madryn indicates a succession in the dominance from Codium spp. to Ulva spp. during the 1990s and from Ulva to Undaria pinnatifida since 1998, accompanied by a significant decrease in biomass of Gracilaria gracilis and Macrocystis pyrifera. The increase of the opportunist species such as Ulva may be supported by the continuous delivery of waste waters into the Nuevo Gulf while the dominance of U. pinnatifida may be associated with port activities. During the sampling period the highest wrack biomass values were recorded in spring and summer. The beach-cast seaweed biomass harvested by the municipality of Puerto Madryn during beach cleaning operation, ranged between 2500 and 12000 t year^–1 ( 200 and 960 t dry weight). Wrack harvesting produces an environmental impact by removing sand from the beach and affecting coastal communities. Composting of wrack is proposed as one of the environmental alternatives to land disposal.     

Two new Aggregata species (Apicomplexa: Aggregatidae) infecting Octopus tehuelchus and Enteroctopus megalocyathus (Mollusca: Octopodidae) in Patagonia, Argentina

During a long-term study carried out between 1981 and 1996 on the biological and fishery aspects of octopuses inhabiting the Gulfs of San Matías, San José, and Nuevo, Patagonia, Argentina, 2 new species of Aggregata (Apicomplexa: Aggregatidae) were found in the digestive tracts of Octopus tehuelchus d'Orbigny, 1834 (prevalence 72%) and Enteroctopus megalocyathus (Gould, 1852) (prevalence 77%). Both species can be distinguished from other congeners on the basis of their hosts, the diameters of sporocysts, and number and length of sporozoites. Despite overlap in the distributions of the two hosts species in the area covered in this study, both Aggregata new species exhibited high host specificity.     

The effect of fertilizer application on farming of the seaweed Undaria pinnatifida (Laminariales, Phaeophyta)

A slow-release ammonium phosphate fertilizer coated with porous plastic was tested on Undaria pinnatifida (Harvey) Suringar as a possible solution to the nutrient deficiency in seawater that causes quality and yield deterioration in seaweed farming. The yield of U. pinnatifida within the fertilized area was 17–40% greater than that of the control area (unfertilized area). In addition, two harvests were possible per season and the quality of harvested U. pinnatifida was also better than that outside the fertilizer diffusion area. The released NH₄-N did not increase the concentration of NH₄-N outside the farming area. Therefore, this fertilizer increased yield and improved quality without causing water pollution.     

Temperature requirements for the growth of young sporophytes of Undaria pinnatifida and Undaria undarioides (Laminariales, Phaeophyceae)

The relative growth rate of young sporophytes of Undaria pinnatifida (Harvey) Suringar and Undaria undarioides (Yendo) Okamura was examined in order to understand the difference in distribution of these two species around the coast of Japan. The optimal temperature for growth of both species was similar at 20°C and the upper critical temperature for growth was also similar, at 27°C for U. pinnatifida and 26°C for U. undarioides. Therefore, the optimal and upper critical temperatures for growth of the young sporophytes are not the main factors determining the distribution of each species. Next, the lower critical temperatures for growth were examined. For the young sporophytes of U. pinnatifida, the lower limit was less than 5°C while for those of U. undarioides it was 15°C. Thus, the difference in the lower critical temperature for growth between the two species was approximately 10°C. During the period of young sporophyte growth in the field, the temperature at the mouth of Ise Bay, Japan, where U. pinnatifida occurs, ranges from 12.7°C in December to 13.1°C in April, with a minimum of 7.9°C in February. Our experiments indicate that young sporophytes are able to grow throughout this period. The temperature off Hamajima, Japan, where U. undarioides occurs, ranges from 19.1°C to 14.8°C during the same time period. Again, young sporophytes are able to growth throughout this period, although minimum winter temperatures are only just high enough for growth. These natural temperature ranges during the growth season of the sporophytes agree well with the experimentally determined temperature requirements for growth of each species. Therefore, the difference between the two species in the critical temperature required for growth of the young sporophytes, especially in the low temperature range, is one of the major factors determining the distribution pattern of each species.