Phytogeographical studies ofCalamagrostis sachalinensis (Gramineae)

Chromosome numbers were determined on 223 collections ofCalamagrostis sachalinensis from 18 localities in Japan. The plants were found to be tetraploid (2n=28), hexaploid (2n=42) or octoploid (2n=56). A few collections were found to include one or two B-chromosomes. The tetraploid collections were made from central Honshu and Mt. Apoi in Hokkaido, while the hexaploids and the octoploids were detected in many localities. Pollen examination of these collections showed that the tetraploids with but one exception have good pollen and the hexaploids and the octoploids have no pollen or have bad pollen with stainability less than 10%. With the help of pollen examination of a number of herbarium specimens, the distribution of the tetraploids and that of the assemblage of the hexaploids and octoploids were delineated. Morphological studies indicated that the tetraploid, hexaploid and octoploid plants can not be separated in gross and spikelet morphology and that the tetraploids in central Honshu and those in Mt. Apoi are significantly different in leaf features. It was concluded thatC. sachalinensis represents an apo-amphimictic complex, which includes the following four races: 1) tetraploid, amphimictic, having thin leaf blades 5–10 mm broad and growing on the subalpine conifer forest belt and the conifer forest-alpine ecotone in the mountains of central Honshu; 2) tetraploid, amphimictic, having hard leaf blades 2–6 mm broad and growing on the stony, arid and exposed alpine belt on Mt. Apoi in Hokkaido; 3) hexaploid, mainly apomictic, the most variable ecologically, widely distributed; 4) octoploid, mainly apomictic, frequent in the upper montane to alpine belts, probably widely distributed.     

Chromosome numbers of the genusCalamagrostis in Japan

Chromosome counts for 783 collection ofCalamagrostis in Japan are reported. These include the first record forC. tashiroi and the reports of new cytotypes inC. stricta, C. hakonensis andC. longiseta. The geographical distribution of different cytotypes ofC. langsdorffii andC. hakonensis is outlined. Counts are also reported for a number of “intermediates” which are supposed to be interspecific hybrids or hybrid derivatives. A summary of chromosome counts for JapaneseCalamagrostis so far recorded is tabulated. No diploid plants with 2n=14 chromosomes are found. The tetraploid taxa, which are plentiful and seem to have adaptively radiated in Japan, jack any sign suggestive of their recent origin from the diploids. It is suggested that plant with 2n=28 (4X in the traditional sense) may be regarded as semidiploid and having that behavior, and that speciation ofCalamagrostis in Japan has occurred principally at this chromosome level. Speciation by means of amphiploidy may have been scarce. It is also suggested that hybridization and polyploidy have greatly contributed to the formation of complicated internal structure of various species.     

Calamagrostis hakonensis (Poaceae): Distribution and differentiation of cytotypes

Chromosome counts were made for a total of 540 collections ofCalamagrostis hakonensis from 66 localities ranging from Kyushu to Hokkaido. Distribution and habitat preferences of the cytotypes involved are described. Sympatric occurrence of tetraploids (=semidiploids, 2n=28) and higher polyploids, as well as that of septaploids and plants at hexaploid and/or octoploid levels, was confirmed in several localities, and mixtures of hexaploids and octoploids within a population were frequently observed. Plants at hexaploid and octoploid levels were the most abundant and widespread. An examination of pollen of the voucher specimens showed that tetraploids (amphimictic) had good pollen, while higher polyploids (apomictic) were generally devoid of pollen and very rarely produced moderately good pollen, the grains of higher polyploids being larger than those of tetraploids. Distributions of tetraploids and higher polyploids were more precisely delineated through an examination of pollen of many herbarium specimens. In relation to the processes by which the complicated internal structure ofC. hakonensis has been established, the following subjects are discussed: infraspecific hybridization between ecotypically differentiated populations, enrichment of variability through occasional sexual reproduction expected in plants with more than 2n=42, persistence of the variants by apomictic reproduction, and probable roles of some extinct taxa.     

A biosystematic study on polyploid populations of the genusSpiraea (Rosaceae) in Korea

A total of 61 chromosome counts from 11 taxa of Korean Spiraea was made. Our counts are the first report for eight taxa;S. blumei (2n=18, 36),S. chartacea (2n=36),S. chinensis (2n=36),S. fritschiana (2n=27, 36),S. microgyna (2n=18),S. prunifolia var.simpliciflora (2n=18),S. pseudocrenata (2n=36), andS. trichocarpa (2n=18). A new chromosome number of 2n=36 (tetraploid) is reported forS. pubescence. Populations of three species includingS. blumei, S. pubescence and .V.fritschiana, show different ploidy levels; diploid and tetraploid populations are found in the former two species and triploid and tetraploid ones, in latter species. Multiplication of chromosome numbers contributes to increase in size of pollen and stomata in the three species. Populations with different ploidy levels inS. blumei occupy different regions; diploid populations in inland Korea and tetraploid ones in Ullung Island. Island tetraploid population of 5.blumei might be originated from intra-island polyploidization through the introduction of diploid from inland Korea, considering the worldwide distribution of this species. Pollen fertilities of island populations of ,S′.blumei are relatively low, and sometimes no pollen grain is produced in anther sacs; it suggests that tetraploid population of the island is gynodioecious which may serve reduction of inbreeding depression.     

Ultrastructural study of spermiogenesis in far-eastern redfins of the genus Tribolodon (Pisces: Cyprinidae)

The spermiogenesis and sperm morphology of the Far-eastern redfins Tribolodon hakonensis (Gunther, 1880), T. brandtii (Dybowskii, 1872), and T. sachalinensis (Okada, Ikeda, 1937) were studied using scanning and transmission electron microscopy. At the spermatid stage, ultrastructural analysis of male germ cells showed no obvious differences between these species. The spermatozoa are primitive acrosome-lacking cells, which are typically found in many representatives of Teleostei with external insemination. Unlike other cyprinids, the angle of inclination of centrioles relative to each other differs slightly in the species under study. The mitochondrial apparatus contains one to five (usually one to three) mitochondria in T. hakonensis, two in T. sachalinensis, and one mitochondrion in T. brandtii.     

Cytology ofCrocus sativus and its allies (Iridaceae)

Populations ofC. cartwrightianus, C. hadriaticus andC. thomasii from the Balkans have 2n = 16 as has the Middle EasternC. pallasii subsp.haussknechtii. C. dispathaceus andC. pallasii subsp.pallasii have 2n = 14 whileC. pallasii subsp.turcicus has 2n = 12.C. niveus has 2n = 28 andC. sativus is an autotriploid with 2n = 24. Karyotype variation was found between populations ofC. pallasii subsp.pallasii in Central Turkey and also inC. pallasii subsp.turcicus.     

Hybridization and evolution inCardamine (Brassicaceae) at Urnerboden, Central Switzerland: Biosystematic and molecular evidence

Hybridization between two diploid (2n = 2x = 16) species ofBrassicaceae, Cardamine rivularis andC. amara, at Urnerboden, Central Switzerland, resulted in the rather unusual triploid hybridC. insueta (2n = 3x = 24), and later on in the amphiploidC. schulzii (2n = 6x = 48). The hybrid and the neopolyploid species colonized successfully some man-made biotopes. Plants ofC. insueta are mostly functional females with non-dehiscent anthers, but true hermaphrodite individuals with partly sterile pollen grains also occur within the population. Analyses of cpDNA and nuclear DNA permitted to establish the parentage of the hybrid: the maternal parent which contributed unreduced egg cells proved to beC. rivularis whereas the normally reduced pollen originated fromC. amara. The pronounced genetic variability inC. insueta revealed by isozyme and RAPD analyses, at variance with the polarized segregation, heterogamy and strong vegetative reproduction of the hybrid, is possibly influenced by recurrent formation ofC. insueta which party results from backcrosses betweenC. insueta andC. rivularis but may also proceed by other pathways. The amphiploidCardamine schulzii has normally developed anthers but its pollen is sometimes highly sterile. The surprisingly uniform genetic make-up of the new amphiploid species might be related to its possible monotopic origin and/or young phylogenetic age but should be further assessed. Site management seems to be very important to a further development of hybridogenous populations and their parent species. In conclusion, the evolution at Urnerboden is discussed in the context of the traditional concept of multiple plant origins.     

Attributes ofCalamagrostis langsdorffii,C. sachalinensis and their intermediates in Shikoku

The internal structure of theCalamagrostis langsdorffii-sachalinensis complex in Shikoku was examined on the basis of a number of new collections. Chromosome counts disclosed the occurrence of the following entities: 6X and 8X, as well as some aneuploids, ofC. longsdorffii; 6X ofC. sachalinensis; 6X and 8X of the intermediates between these two species. The examination of pollen of these collections and the herbarium specimens showed that all of them may be apomictic in seed formation and that the sexual tetraploids of the pertinent complex may not be distributed in Shikoku. Details of morphological features of the collections were analyzed, and the intermediacy in morphology of the group “intermediate” was confirmed by the distance diagram method. The collections ofC. langsdorffii from Shikoku generally showed an awn longer than that of the collections from Honshu and Hokkaido. On the basis of these and some other observations, relationships of the strains extant in Shikoku were discussed. For the derivation of the present-day composition of the pertinent complex, an hypothesis which is founded on the presumption of a past occurrence of sexual tetraploids of bothC. langsdorffii andC. sachalinensis in Shikoku has been advanced.     

Natural hybridization in JapaneseCalamagrostis

Relationships amongCalamagrostis longiseta var.longiseta, C.l. var.longe-aristata andC. fauriei, which are principally at the 2n=28 chromosome level, were studied mainly on the basis of population samples. The populations comprised (1) “pure” populations of each ofC.l. longiseta, C.l. longe-aristata andC. fauriei and (2) populations showing a gradation fromC.l. longiseta toC. fauriei via the intermediateC.l. longearistata and fromC.l. longiseta toC.l. longe-aristata. Hybridization betweenC.l. longiseta andC. fauriei was estimated to be ultimately related to the geneses of the population structures detected, and it was concluded thatC.l. longe-aristata must be of hybrid origin betweenC.l. longiseta andC. fauriei. Populations showing a gradation fromC.l. longiseta toC.l. longe-aristata were regarded to have been brought about by the extinction ofC. fauriei from the hybridizing population coupled with the change of environments and also by the secondary contact betweenC.l. longiseta and plants ofC.l. longe-aristata migrating from the area that produced it. No significant reduction of pollen fertility and seed productivity was found inC.l. longe-aristata. Based on the results of population analyses, the delimitation of the taxa concerned was made clearer. The examination of herbarium specimens showed that the range ofC.l. longe-aristata considerably exceeds the overlapping area of the present ranges ofC.l. longiseta andC. fauriei. The three taxa were deviated ecologically, and “pure” populations ofC.l. longe-aristata were found on several damp subalpine fields in central and northern Honshu that seemed to represent the most suitable niche for this taxon. It was estimated thatC.l. longe-aristata would evolve into a new good species if the future organism-environment interactions are favorable for it.     

New chromosome numbers for plant taxa endemic to the Balearic Islands

Mitotic chromosome numbers are reported from 25 vascular plant taxa, endemic to the Balearic Islands that are poorly known cytogenetically. The chromosome numbers ofAnthyllis vulneraria subsp.balearica (2n=12),Cymbalaria fragilis (2n=56), andPolygonum romanum subsp.balearicum (2n=40) were determined for the first time. A new chromosome number was found in several populations ofAnthyllis hystrix (2n=70) suggesting that this species is decaploid, in contrast to an earlier work reporting a higher ploidy level (2n=12x=84). The new chromosome number 2n=32 was reported inHypericum hircinum subsp.cambessedesii. It is suggested that the previous count (2n=40) could be explained by the presence of anomalous pentaploid cells in some tissues, contrating with the presence of a regular tetraploid complement (2n=32). Cytogenetic observations suggest thatSibthorpia africana has a diploid chromosome complement of 2n=18, with 0–2 accessory chromosomes. Accessory chromosomes are also reported forPhlomis italica, being the first record of B chromosomes in this genus. Chromosomal instability was found inGalium crespianum andG. friedichii species, with three numbers 2n=44, 55 and 66. Two cytotypes differing in ploidy level were documented within single plants. It is suggested that both species share a regular complement of 2n=44 and that the past hybridization events and formation of regenerating roots from the typical rootstock ofG. crespianum andG. friedrichii could be involved in the genesis of chromosome variants through partial endopolyploidy and concomitant somatic segregation.     

Natural hybridization in JapaneseCalamagrostis

Taxonomic relationships betweenCalamagrostis langsdorffii andC. sachalinensis were investigated in connection with the discovery that a considerable number of plants intermediate between these species occur in the high mountains of central Honshu. The studies were mainly carried out on the basis of cytological voucher specimens for which a chromosome number was known. Their morphological features, leaf flavonoids and pollen grains were subjected to examination. Hybridization, polyploidy and gametophytic apomixis are related to the organization of this complex, and plants referable to the “intermediates” are apomictic octoploids superimposed on the ancestral and sexual tetraploid taxa. The internal structure of this complex is discussed together with its probable course of evolution, and a diagram showing the outline of the structure is presented. The variability of morphological features and flavonoid patterns of the plants concerned is examined, and the delimitation ofC. langsdorffii andC. sachalinensis is made clearer.     

Serpentine and polyploid differentiation withinGalium pumilum agg. (Rubiaceae) in Eastern C. Europe

The local differentiation of a model group,Galium pumilum agg., was studied in serpentine versus non-serpentine habitats in the Czech Republic and adjacent regions in Austria, Germany and Poland. Serpentine habitats form ecologically distinct islands within the landscape; local micro-evolutionary processes may be important there, both because of small population sizes and the strong selection effects of the metal-rich soils. TheGalium pumilum agg. is a group of taxa showing typical karyological and ecological differentiation; the following species and cytotypes were studied:Galium pumilum Murray (2n=8x=88),G. valdepilosum Heinr. Braun (2n=2x=22, 2n=4x=44),G. sudeticum Tausch (2n=4x=44) andG. austriacum Jacq. (2n=4x=44). The karyological and taxonomic investigation showed that serpentine versus non-serpentine habitats do not play an important role in the differentiation of the species studied. (1) The examined populations ofG. pumilum Murray were homogeneous in chromosome numbers, belonging to the octoploid (2n=88) cytotype only. (2)G. valdepilosum consists of two cytotypes. Both of them occur on and off serpentine sites, but they show pronounced East-West distributional difference. (3)G. sudeticum occupies special localities on serpentine in western Bohemia, which are geographically isolated from its nearest localities in the Krkono?e Mts. The plants coming from both localities belong to the tetraploid cytotype. (4) A highly polyploid plant (2n=12x=ca. 132) from theG. pumilum group was found on serpentine. From the methodological point of view, pollen size turned out to be reliable only for distinguishing octoploids from diploids and tetraploids, but it is less suitable for separating the latter two ploidy levels. The occurrence ofG. austriacum is reported for the Czech Republic for the first time with certainty. This record extends the known distribution area ofG. austriacum in the NW direction.     

Demographic traits of understory trees and population dynamics of aPicea-Abies forest in Taisetsuzan National Park, northern Japan

The size structure transition matrices ofPicea jezoensis, Picea glehnii andAbies sachalinensis of a sub-boreal forest in Hokkaido, northern Japan were constructed based on the demography of each species (Picea jezoensis andPicea glehnii were dealt with together asPicea) during a 4-year period. Two types of matrices, density-independent and density-dependent population dynamics models, were investigated for evaluating the ‘waiting pattern’ betweenPicea spp. andA. sachalinensis. For the density-dependent model, it was assumed that the demographic traits of understory trees, the recruitment rate, the understory mortality rate and the transition probability from the understory to canopy stages, were regulated by the one-sided competitive effect of canopy trees. The observed size structure ofPicea was almost consistent with the stationary size structure obtained in both the density-independent and the density-dependent models, whereas the observed size structure ofA. sachalinensis was not realized in the two models. The effects of both the transition probability from the understory to canopy stages and the recruitment rate on the dynamics of canopy trees were investigated. ForPicea, two parameters—recruitment rate (e _i ) and transition probability from the understory to canopy stages-exponentially affected the dynamics of canopy trees. In contrast, forAbies sachalinensis, the two parameters affected linearly the dynamics of canopy trees. In conclusion, the population dynamics ofPicea andA. sachalinensis was determined by the parameters of the recruitment rate and the transition probability from the understory to canopy stages, relating to waiting patterns of understory trees for future gap formation. InPicea, the demographic parameters of understory trees intensively regulated the dynamics of canopy trees if compared withA. sachalinensis, suggesting that the performance of understory trees plays a key role in the population dynamics ofPicea. This reflects the growth pattern of understory trees in the regeneration of the two species.     

Taxonomic features ofSesleria calabrica (Poaceae), a neglected species from southern Italy

A taxonomic study of theSesleria juncifolia complex in the Italian Peninsula is presented, with a focus on southern Italian populations here named asSesleria calabrica (Deyl)Di Pietro comb. nov. et stat. nov. Karylological, morphological and anatomical characters were used for comparative analyses with populations of closely related species, such asS. juncifolia Suffren andSesleria apennina Ujhelyi occurring in the Italian Peninsula. Multivariate and univariate morphometric analyses, and qualitative morphological characters showed a distinct position ofS. calabrica. Populations ofS. calabrica differ in respect to various morphological characters of leaf and spikelet, such as the glume, lemma and palea length, stem length, the leaf sheath, leaf width, leaf thickness, and the total number of vascular bundles. Furthermore, previous karyological studies demonstrated that all the populations of bothS. juncifolia andS. apennina examined are octopolid (2n=8x=56), whereasS. calabrica was found to be dodecaploid (2n=12x=84).S. calabrica is strictly confined to the Pollino massif and the Orsomarso mountains in southern Italy, which represent the southernmost limit of theSesleria juncifolia complex distribution area both in Italy and in Europe. In addition toS. juncifolia andS. calabrica, the recognition ofS. apennina as a taxon distinct fromS. juncifolia is supported, at least for the area of the Apuan Alps.     

Ploidy variation in the group ofMyosotis palustris andM. laxa in the Czech Republic and Slovakia

In 74 natural populations of theMyosotis palustris andM. laxa groups from former Czechoslovakia three euploid and one aneuploid cytotypes were found that belong to the following species:M. nemorosa Besser, 2n=22,M. palustris (L.)Nath. em.Reichenb. inSturm, 2n=66,M. laxiflora Reichenb., 2n=66,M. radicans Opiz, 2n=66(64),M. brevisetacea (Schuster) Holub, 2n=66(64), andM. caespitosa C.F. Schultz, 2n=88. With the exception ofM. nemorosa, the chromosome numbers are published for the first time for the Czech Republic. The chromsome numbers, 2n=66, 2n=64 are found inM. brevisetacea, are new for the literature. The correlation between pollen size and ploidy level has been studied as well, and statistically significant differences were found between cytotypes belonging to different ploidy levels.     

Differences in the life histories of twoCochlearia species

Cochlearia bavarica Vogt andC. pyrenaica Dc. are closely related and highly endangered species in Bavaria (SE Germany).Cochlearia bavarica (2n=36) is a hybrid ofC. pyrenaica (2n=12) andC. officianalis (2n=24) stabilized by polyploidy.Cochlearia officinalis does not occur in Bavaria. The question being addressed is whether the present non-overlapping distribution of the two Bavarian species, both of which are restricted to calcareous springs with a continuous water supply or drainage ditches, is due to competitive exclusion or to subtle differences of ecological requirements. I did not find any evidence for the second case, i.e. niche differentiation, because both species occurred in all the habitat types that I could define by floristic and ecological criteria. The population structures of bothC. bavarica andC. pyrenaica vary in parallel with different habitat types. Both species have the greatest reproductive output (viable seeds) and the highest population densities in habitats with high light availability and/or low interspecific competition. Thus, I expected that one of the two species might be competitively superior over the other, but that it would fail to reach all its potential sites of occurrence. Cochlearia bavarica individuals (dry mass =5.75 g) grow significantly larger thanC. pyrenaica individuals (3.62 g;P<0.05) and produce more, larger and heavier seeds, possibly due to hybrid vigour. Flowering individuals ofC. bavarica also allocate more biomass to vegetative structures thanC. pyrenaica. The analysis of population dynamics reveals a higher life expectancy and reproductive output inC. bavarica. The calculated population growth rates although negative over the observation period in both species, suggest a significantly higher fitness ofC. bavarica (λ=0.66) compared withC. pyrenaica (λ=0.44). Thus, our data are in line with the competitive exclusion hypothesis andCochlearia bavarica appears as an example of a species with hybridogenous origin possessing higher fitness than its progenitor. However, considering the rarity of both species it seems at present unlikely that the former will displace the latter over a large distributional region.     

The vegetation of central yacutian alases

Alases are unique grassland landscapes in Central Yacutia, their development influenced by extra-continental arid climate. Twenty three associations have been distinguished and described. These associations form an ecological series from steppe withFestuca lenensis andStipa krylovii through salt and swamp meadow (Hordeum brevisubulatum, Puccinellia tenuiflora, Alopecurus arundinaceus, Calamagrostis langsdorffii, Carex juncella) to swamp communities ofScolochloa festucacea, Glyceria triflora, Scirpus lacustris andTypha latifolia. The community complexes of specific elements of alas landscapes—baidjerakhs and bulgunnyakhs—are analysed.     

The internal transcribed spacer 2 region of the nuclear ribosomal DNA and the phylogeny of the moss family Hylocomiaceae

Eichhornia azurea is a tristylous species of Pontederiaceae. Moderate self-incompatibility accompanies the floral heteromorphism of this species.Eichhornia azurea is almost exclusively visited by one bee species,Ancyloscelis gigas (Anthophoridae), in South Brazil. This species has an extremely long proboscis covered with recurved hairs. Bees use these hairs to collect pollen from the anthers placed inside the narrow perianth tube ofE. azurea. Analyses of the pollen load ofA. gigas females show that they are flower constant and carry pollen from all three anther levels. The behavior ofA. gigas and its proboscis morphology make this bee species narrowly adapted and an effective pollinator for facilitating legitimate pollination ofE. azurea flowers in southern Brazil.     

Introgressive hybridization between a native and an introduced species:Viola lutea subsp.Sudetica versusV. Tricolor

A hybrid swarm betweenViola lutea subsp.sudetica (2n=50, native species) andViola tricolor (2n=26, introduced species) originated in the 1970’s in the Krkono?e Mts. Analyses of chromosome numbers, reproductive biology, morphology, and ecology gave the following results: (1) Compared to the plants found in the 1970’s, the number of colour morphs have decreased and the types now prevailing in the field are morphologically closer toV. lutea subsp.sudetica, forming a continuum. (2) In the field, hybrids having approximately the same chromosome number as the primary hybrids are most common. Some plants of the hybrid swarm have certain characters unknown to their parents. (3) In the field, autogamous types similar toV. tricolor were found. (4) A limited number of plants from the field and culture have higher somatic chromosome numbers thanV. lutea subsp.sudetica; there was a tendency towards increasing chromosome numbers in their progeny (up to 2n=62). These plants have some new morphological characters (a small proportion of hexacolpate pollen) not found in the parents (nor in the other hybrids with prevailing tetracolpate and pentacolpate pollen grains) and higher pollen fertility in comparison to the other hybrids. These plants also have the highest germination rate. (5) There is a tendency for chromosome numbers to decline in the progeny of open pollinated hybrid plants in the lowland experimental graden. (6) The phenology of the plants in the mountain grasslands and the lowland garden is different; the parents behave in a totally contrasting manner. (7) In the field at least some hybrids extend outside the geographical and ecological ranges of the parental species, invading new communities. (8) Seeds ofV. tricolor do not show any dormancy and germinate in the year of production; most of theV. lutea subsp.sudetica seeds germinate during the spring of the following year. Hybrids with intermediate chromosome numbers had both types of germination strategy. The germination rate of intermediates with high chromosome numbers was even higher than that ofV. tricolor.     

Investigation and documentation of hybridization betweenParkinsonia aculeata andCercidium praecox (Leguminosae:Caesalpinioideae)

Morphometric, cytogenetic, geographical and ecological evidence for hybridization betweenParkinsonia aculeata andCercidium praecox is presented. Morphometric investigation using the character count procedure and cytogenetic observations confirm hybrid status. All diagnostic morphometric characters were intermediate in the hybrid. Both parents (2n = 28) show regular tetrad formation and pollen fertility greater than 94%. Hybrids have a chromosome number of 2n = 28 or 2n = 30, and display meiotic abnormalities including lagging chromosomes and micronucleus formation; less than 21% of hybrid pollen was fertile. Ecological and geographical information suggests that hybridization is occurring at increasing frequency due to the expanding range ofP. aculeata associated with cultivation as an ornamental, coupled with ecological disturbance and weediness, and the cultivation ofC. praecox and hybrids as fodder, ornamental and shade trees. Hybrid fertility and phenological observations, in conjunction with F-weighted principal component analysis, suggest that the progeny of F₁ hybrids are established. The hybrid is formally described asP. ×carterae.