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Der “Kryptospezies”-Begriff zur Kennzeichnung genetisch isolierter allopatrischer Populationen einer Morpho- und Ökospezies am Beispiel von Rhabditis spiculigera (Nematoda)
Journal of Zoological Systematics and Evolutionary Research
Abstract
Bei der kosmopolitischen Rhabditis spiculigera wurde Interfertilität zwischen Populationen von Hawaii und Neuseeland festgestellt, dagegen eine vollständige reproduktive Isolation zwischen diesen beiden Populationen und solchen aus Europa. Dieser Nachweis der Entstehung von Isolationsfaktoren ohne Abänderung der Morphologie oder Ökologie regt zur Erörterung des Spezieskonzepts bei allopatrischen Populationen an, wobei die durch stabilisierende Selektion der ökologischen Nische gleichförmig gehaltene Ökospezies wichtiges Kriterium ist. Reproduktiv isolierte allopatrische Lokalpopulationen solcher einheitlicher Morpho- und Ökospezies werden als, Krytospezies' einer Art bezeichnet (ohne nomenklatorischen Status). Ihnen kommt ein wichtiges Attribut guter Arten zu (Isolationsfaktoren), während die ökologische Sonderung (unterschiedliche Einnischung) noch fehlt. Dies unterscheidet sie von Zwillingsarten, aber auch den ökologisch-morphologisch divergenten Semispezies mit nur partieller Isolation. Die unterschiedlichen Schritte allopatrischer Speziation (über Krytospezies bzw. Sub- und evtl. Semispezies) werden in einem Schema gegenübergestellt.
... The term 'cryptic species' which has been used to describe the different morphotypes of X. intermedia, is in some respects a delusive term: Sudhaus (1978) coherently defined two cryptic species (in German 'Kryptospezies') as two reproductively isolated allopatric populations without any morphological or ecological segregation compared to each other. The other case, two allopatric populations with clear morphological and ecological differentiation but without or only incomplete reproductive isolation, is called a subspecies. ...
... The other case, two allopatric populations with clear morphological and ecological differentiation but without or only incomplete reproductive isolation, is called a subspecies. Both scenarios can lead to biospecies if 1) cryptic species differentiate morphologically and ecologically and if 2) complete reproductive isolation evolves between two subspecies (Sudhaus 1978). According to this definition, all reported muscular morphotypes of X. intermedia would at least represent subspecies since the authors present clear-cut morphological differences that legitimate the erection of separate morphospecies. ...
... This interfertility is astonishing, as gene flow between widely separated populations can be excluded. In other cases of apparently cosmopolitan morphospecies, crossing experiments or DNA analyses have revealed an underlying assemblage of cryptic species ( Litoditis " marina " superspecies, Mesorhabditis " spiculigera " , species of the Caenorhabditis Elegans-group), replacing each other allo-or ( Litoditis) even parapatrically and in their ecological function (Derycke et al. 2008, Sudhaus 1978a, Kiontke et al. 2011. Noteworthy are pairs of closely related species where the first lives in tropical areas and the second in the temperate zone, such as Caenorhabditis brenneri -C. ...
... In most cases, these differences are correlated with morphological differences, some times only minute ones. If we are not able to find such morphological differences, we call these ethospecies or forms cryptospecies (Sudhaus 1978). However, cryptic species are in many cases depending on the "spectacle of the observer". ...
It is demonstrated that the biological species concept of the genus Ophrys corresponds to the general concepts of Ernst Mayr. On the example of two closely related forms of the fusca group in Andalucia, it is shown how to handle the different criteria of the biospecies concept. One is the high specifity of attraction of a male bee followed by a complex pseudocopulation behaviour which enables the correct pollen transfer within the species. The high specifity is caused by a highly remarkable imitation of the sexual pheromones of the mimicked female of the pollinator. Sexual pheromones of animals act as intraspecific signals which result in attractions of only males of the same species. Exactly this specific behaviour is triggered by the Ophrys flower, too. Thus the pollinator male is attracted only to those flowers which have the correct mixture of the pheromone molecules. To further ensure success the pollinating males also select other characters of the Ophrys flower as labellum size, colour, labellum hair characters, phenology and possibly habitat selections etc. In the sexual reproduction behaviour of the male insect acts as pregamic isolation mechanisms for the given Ophrys like for their own female.
We were successful in confirming the high specifity of the pollination mechanisms in numerous field experiments, mainly choice experiments, this in contrast o the statements of Hennecke & Munzinger. They had argued that there were many different pollinator species listed in the literature for a given Ophrys species. However, they did not critically assess the reliability of these citations. For this, they would have had to ctitically read the primary literature and not only the secondary quotations like in Delforge or others. Therefore, they rehashed many of the old mistakes concerning wrong identifications of the bees or even the Ophrys taxons which had long been corrected. Especially a mixture of old and actual names of the same species in different combinations is annoying and seems to demonstrate that the authors are not really fit in the nomenclature of Ophrys and their pollinators. This is demonstrated by some examples, which are very confusing without knowledge of the bees. For example, these authors did not realize that a 3-4 mm bee (Andrena hesperia) could not serve as a pollinator of a 20 mm labellum of a large Ophrys omegaifera species.
However, there are some cases with more than one pollinator. Besides the main pollinator the others I call them “secondary pollinators” which in those cases we could check their pollination contribution in the population is very weak. In many cases, these secondary visitors are mainly pollinaria thieves because they are only attracted and try to copulate. However, they seem to learn very quickly that Ophrys is not a true female and will never visit another flower of this kind. In some quantitative field experiments (with Eucera nigrescens/longicornis on Ophrys holosericea) we could confirm this hypothesis. The conclusion of the two authors that Ophrys species are not species-specific regarding sexual attractivity does not correspond to our field experiments regarding olfactory compound investigations in biotests, and does not agree with the molecular data of population biology and with the genetic analyses. The other proof the authors used in their argumentations are the supposed frequency of hybrids. But this is also a spurious argument. Hybrids are only frequent in literature and not in nature. In places frequently visited by orchid enthusiasts, the number of observed “hybrids” is conspicuously high, which may indicate “hand pollination”.The aim of the two authors has been to reduce the many species within Ophrys because they cannot be discriminated. Consequently, they try to establish a simplified classification system without any biological background. A complete anthropomorphic typological systematic like the “Index of accepted plant names” is issued by Kew Gardens. However, this is in the 21. Century, 150 years after Darwin, a kind of middle age taxonomy. They use a quite typological morphospecies concept like in the book of Pederson & Faurhold (2007). This does not fit with nature. If you pay attention to the different criteria of the biospecies concept within the genus Ophrys you will recognise the many species which the genus makes so interesting. A critical list of the known pollinators of the genus Ophrys is given as an appendix.
Rakosy, D., Paulus, H.F. & M. Hirth (2020): Ophrys dimidiata, a hitherto
undescribed species of the Ophrys tenthredinifera complex in Crete
(Orchidaceae).- J. Eur. Orch. 52 (1): 207-226.
According to current knowledge there are three different species within the
Ophrys tenthredinifera complex on the island Crete. DELFORGE (2005) had
described two of them as O. dyctinnae and O. leochroma, whereas he assigned
the third species to the eastern Mediterranean O. villosa. We conducted
pollinator observations and biotests, proving that each taxon is exclusively
pollinated by a different pollinator. Thus, Eucera albofasciata pollinates
O. dyctinnae and Eucera kullenbergi O. leochroma. Whereas, the pollinator of
the third taxon assigned by Delforge as O. villosa is Eucera dimidiata.
However, the eastern Mediterranean O. villosa like O. tenthredinifera s.str. in
the western Mediterranean area is pollinated by Eucera nigrilabris. Therefore
and because of its disjunct distribution and sligtly different morphology,
O. villosa has to be classified as a geographical subspecies of the nominate
species, O. tenthredinifera subsp. villosa. The Cretan species within the
Ophrys tenthredinifera complex which Delforge assigned to O. villosa is a
hitherto undescribed species, which we describe as Ophrys dimidiata. The
name is derived from its pollinator Eucera dimidiata. This green-eyed longhorned
bee is common in North Africa, the Near East, and Cyprus and has its
only European occurrence on the island of Crete. Ophrys dimidiata is endemic
to Crete, whereas O. tenthredinifera subsp. villosa and its pollinator bee
Eucera nigrilabris are lacking on this island. The description of O. dimidiata
Autorenexemplar - copyright by AHO Baden-Württemberg
208 Journal Europäischer Orchideen 52 (1): 2020.
as a separate species and classification of O. villosa as a subspecies of
O. tenthredinifera are further supported by chemical and morphological data.
Rakosy, D., Paulus, H.F. & M. Hirth (2020): Ophrys dimidiata, a hitherto undescribed species of the Ophrys tenthredinifera complex in Crete (Orchidaceae).- J. Eur. Orch. 54 (1): 207-226.
According to current knowledge there are three different species within the Ophrys tenthredinifera complex in Crete. DELFORGE (2005) had described two of them as O. dyctinnae and O. leochroma, whereas he attributed the third species to the Eastern Mediterranean O. villosa. We conducted pollinator observations and biotests, proving that each taxon is exclusively pollinated by a different pollinator. Thus, Eucera albofasciata pollinates O. dyctinnae and Eucera kullenbergi O. leochroma, whereas, the pollinator of the third taxon is Eucera dimidiata. O. villosa is pollinated by Eucera nigrilabris like O. tenthredinifera in the Western Mediterranean area. Therefore, O. villosa belongs to the typical O. tenthredinifera. Its disjunct distribution and sligtly different morphology in the Eastern Mediterranean area suggest it being a geographical subspecies of the nominate species, O. tenthredinifera subsp. villosa. The Cretan O. villosa of Delforge is a further different entity, which we describe as Ophrys dimidiata; the name is coming from the pollinator bee species Eucera dimidiata. This long-horned bee with green eyes is distributed in northern Africa, the Middle East, Cyprus and has its only European occurrence on the island of Crete. Ophrys dimidiata is endemic to Crete, whereas O. tenthredinifera subsp. villosa and its pollinator bee Eucera nigrilabris are lacking on this island. The description of O. dimidiata as a separate species and classification of O. villosa as a subspecies of O. tenthredinifera are further supported by chemical and morphological data.
Die Realität der Art wird begründet und die Frage nach ihrer biologischen Bedeutung gestellt. In diesem Zusammenhang wird der jeweilige Anpassungsvorteil von Agamo- bzw. Biospezies gegenübergestellt. Der Artbegriff als zentrales Konzept der gesamten Biologie berücksichtigt die relative Konstanz ebenso wie die Veränderlichkeit in der Generationenfolge. Die Eigenständigkeit der evolvierenden Art und ihr historisch gewachsener Informationsgehalt werden aufrechterhalten durch genetische Homöostase und stabilisierende Selektion der spezifischen ökologischen Nische (Aspekt der Okospezies) und einen durch Fortpflanzungsisolation gegenüber anderen Gruppen geschützten gemeinsamen Genpool (Aspekt der Biospezies).
The importance of the species concept in biology has led to a continuing debate about the definition of species. This paper summarizes the recent literature in relation to the ‘biological species concept’ (MAYR 1942). Among the general attributes demanded, possible limitations of the universality and applicability of a species definition are discussed. Three different areas of criticism of the biological species concept are considered: 1. The impracticability of the criterion of reproductive isolation. The demand for more practical criteria is rejected, because reproductive isolation is seen as the factor that produces and maintains species as discrete entities in nature. 2. The inapplicability to non-bisexual organisms. A brief survey of modes of uniparental reproduction and their relative importance suggests that obligatory apomicts are of little evolutionary significance. 3. The inapplicability to multidimensional situations. Despite practical difficulties, the biological species concept is held to apply to organisms separated in space. The impossibility to delimit species in time by reproductive isolation is recognized. Out of two ways to divide continuous evolutionary lineages in time, the phylogenetic approach, which considers only speciation events (cladogenesis), is preferred as it is more objective. A list of recently published alternative definitions of species, none of which is found acceptable, is given. It is concluded that the biological species concept needs not be changed or dismissed on the basis of the discussed criticisms.
Recessive albino mutants occur in natural populations of several species of planorbid molluscs. These mutants have been used as genetic markers in experiments planned to place the systematics of this family on a sound biological basis. These experiments have yielded the following general conclusions. 1. A snail grown in isolation freely reproduces by self-fertilization, but this process is readily and completely replaced by cross-fertilization if the snail is placed with another conspecific individual from the same population. 2. Cross-fertilization does not entirely replace self-fertilization in mates between conspecific allopatric individuals. Such crosses result in a lowered production of hybrid offspring. However, the fertility of the snail is kept unimpaired, owing to self-fertilization of those eggs which failed to be cross-fertilized. This fact indicates that the lowered interfertility depends on variable degrees of gametic isolation rather than on any cytogenetic mechanisms. 3. All the recognizable morphological species so far studied by us have shown absolute reproductive isolation. 4. In spite of the planorbids being hermaphrodites perfectly capable of self-fertilizing, their colonies must be regarded as Mendelian populations in the same sense as those of dioecious organisms. 5. It seems that geographic speciation is paramount also in the evolution of the planorbids. However, it is possible that the faculty of self-fertilization may favor in some special cases also sympatric speciation.
The behaviour of small populations ofPytilia phoenicoptera andP. lineata living together in a spacious aviary, was investigated during three successive breeding seasons. The pair-formation of the offspring was closely observed.
Phoenicoptera andlineata live geographically isolated and differ mainly in the colour of the beak, which is black inphoenicoptera and bright red inlineata. Behaviour and voice are almost identical in both forms.
The offspring from both populations mated only with birds of the same form. Interbreeding did not occur either, if in one form males were more numerous than females, and in the other vice versa. The odd birds out tried to join up with the conspecific pairs and showed no interest for the single birds of the opposite sex in the other population.
The rigid reproductive isolation betweenphoenicoptera andlineata in captivity suggests that they would not interbreed under natural conditions either.Pytilia lineata must therefore, be recognised as a independent species; it cannot any more be regarded as a geographic race ofPytilia phoenicoptera.
Within the genusPytilia, as in many other Estrildidae, the red beak colour and/or red head-mask is a species recognition and aggression releasing signal. Male aggression releasing signals in most cases simultaneously release sexual behaviour in the females. From these two facts, it may be indirectly concluded that the red beak colour oflineata acts as the decisive isolating factor between it andphoenicoptera.
It is suggested that morphological or behavioral characteristics, which act to produce reproductive isolation in allopatric forms should be termed potential isolating factors, not isolating mechanisms.
The presence of western, eastern, and northern call types of the Rana pipiens complex in Illinois supports evidence from the western United States that this complex can no longer be regarded as one species.
Systematik und Stammesgeschichte der Tiere 1954-1959
- Gunther