Affinis WATCH Newsletter Special Issue - April 1997
W
elcome to this special edition of Affinis WATCH. It is devoted to one article that was originally written for inclusion in the Pteridologist. It was considered to be too technical for the target readership so we decided to publish it here. ACJ & ACP.
Morphotypes of the "Dryopteris affinis" complex in Britain and Ireland Anthony Pigott I had previously decided to resist the temptation to publish anything until the systematic position of the 'D. affinis' complex was firmer. However, there is an increasing demand for information, not satisfied by existing publications, from the growing number of botanists that want to identify what they find in the field. This, coupled with the mis-representation of the morphotype approach recently published in the Fern Gazette, has changed my mind. This article covers why I believe it is currently best to use the 'morphotype' approach and gives comparative descriptions of the best known morphotypes in the accompanying tables. It is necessarily brief and informal but I intend to present a full treatment of the morphotypes later this year. Only morphotypes that occur in Britain and Ireland are covered here. There are a number of others known from elsewhere, mainly Europe. The distribution of the 'D. affinis' complex is concentrated on the Atlantic coast of Europe and consequently these small islands have more than their fair share of both individuals and taxa. We are very lucky that it is so! So, why use morphotypes? In summary, it is because the treatment of the complex as a single species made up of various sub-species and varieties is unsatisfactory and because, at present, any other treatment within the formal rules of nomenclature would be too uncertain and therefore likely to be transitory. There are known to be at least three distinct genome combinations in the "D. affinis" complex. Although the definition of a species can be a difficult issue, there is no species concept based on biological or evolutionary principles that would support treating all of these entities as one species. It has been suggested that an artificial approach is necessary because of the difficulties in identifying specimens. It seems clear to me that the description of species should reflect the biological reality, not the currently assumed ability of people to distinguish them. I do not feel that, at present, we have enough hard scientific evidence to have a high level of confidence in the underlying genetic origins. Without this, any formal systematic treatment is based on poor foundations and consequently likely to change when new evidence arrives. There have been numerous published versions of the D. affinis single species treatment over the years, with changing groupings of sub-species and varieties. All of this has produced a large number of synonyms and misidentifications that can cause confusion and which now have to be dealt with in any subsequent taxonomic work.
The suggestion that all the variation in Britain and Ireland can be readily assigned to three sub-species is not consistent with what seems to be the experience of most botanists that have seriously studied the complex. The variation within each of these 'sub-species' is too great to allow any simple but accurate key to be devised and there are distinct entities within subspecies that are, at least superficially, more like other 'subspecies' than they are like the remainder of their own. An attempt to 'shoe-horn' all the specimens into these three 'subspecies' is likely to result in significant misidentification and loss of information about the true variation and its distribution. For example, morphotype paleaceo-lobata is regularly misidentified as 'subsp. cambrensis' by those following subspecies accounts and keys. Although there have been quite a large number of cytological examinations within the complex, unfortunately almost all of them have been on the more common morphotypes which are most representative of the 'sub-species'. For example, the very distinct morphotype kerryensis has never, to my knowledge, even had its ploidy level determined; it is assumed to be diploid and put in 'subsp. affinis' on the subjective assessment of its morphology. The use of morphotypes to describe the entities found in nature means that useful working names can be applied without the formal nomenclatural implications. These morphotypes may represent varying degrees of difference, genetic and genomic. They are treated equally as just being the distinct morphological units to which individual plants can be ascribed. We can study the range of variation within the morphotypes and understand their geographical and ecological distribution. When our understanding of the evolutionary history of the complex is more complete and stable, formal names, probably three or more species, with sub-species and varieties to cover significant regional and local variation within the species, can be given and hopefully would last. I believe that taxonomists have a responsibility to be cautious about formally publishing new names. There is already considerable frustration by horticulturalists, naturalists and other biologists about the way names change without apparent good reason. This is especially true when the changes are due to often obscure technicalities and the unearthing of longforgotten publications. We should remember that the purpose of the codes is to provide consistency and stability in the naming of organisms. The study of names should not become an end in itself and we should prevent the nomenclatural tail wagging the systematic dog. The use of morphotypes in the analysis of the 'D. affinis' complex is not an attempt to avoid the use of formal nomenclature; it is merely a way of enabling discussion of the natural taxa found in nature without currently adding any more potential synonyms until we are sure of the biology. The morphotypes described here are distinct morphological taxa representing plants that form large populations and have an extensive distribution. They are all well known to me from the field and from plants I have in cultivation. All the descriptions are from my own observations although I have reviewed them against the various other accounts that are available. The names largely follow existing usage of published varietal names in the complex. Strictly speaking, the names could have been anything but it seemed perverse not to use those already around. However, this does not imply that I believe that these would
Published by the B.P.S. Mapping Project, British Pteridological Society, c/o Department of Botany, The Natural History Museum, Cromwell Road, LONDON SW7 5BD ISSN 1368 - 6372
Comparative Descriptions for 'Dryopteris affinis ' complex in Britain & Ireland Morphotype
Anthony Pigott
affinis
convexa
paleaceolobata
kerryensis
cambrensis
arranensis
borreri
robusta
insolens
Lamina shape
lanceolate to ovate
lanceolate to ovate
lanceolate to ovate
narrowly elliptical
lanceolate to ovate
lanceolate to ovate
tapering-truncate
tapering-truncate
tapering-truncate
tapering-truncate
oblanceolate to narrowly elliptical tapering-truncate
lanceolate to oblong
Lamina base
oblanceolate to narrowly elliptical tapering
truncate
tapering-truncate
truncate
Lamina texture
glossy, 'plasticcoated', stiff
very glossy, stiff
glossy, crisped, stiff
glossy, stiff
somewhat glossy, slightly crisped, stiff
only slightly glossy, not stiff
only slightly glossy, not stiff
only slightly glossy, not stiff
only slightly glossy to somewhat glossy, not stiff
Frond persistence
lasting with little damage until spring
lasting with little damage until spring
lasting with little damage until spring
dying-back dying-back rapidly progressively through after first frosts winter
dying-back rapidly after first frosts (not well known)
dying-back dying-back dying-back progressively through progressively through progressively through winter winter winter
narrowly oblong, tapering from midlength to acuminate tip
narrowly oblong, tapering from midlength to somewhat acuminate tip
narrowly oblong, tapering from midlength to somewhat acuminate tip
narrowly oblong, tapering to shortly acuminate tip
narrowly oblong, tapering to shortly acuminate tip
somewhat rolledunder or 'crimped', slightly tapering, strongly round lobed to round-rectangular lobed
even, flat, roundtips often turned-up, more or less even, rectangular lobed (but tapering, round-lobed somewhat round often scarcely lobed) lobed (but often scarcely lobed)
Character
Pinna shape (mid blade) narrowly oblong, tapering from midlength to long acuminate tip Pinna-segment shape
even, flat, roundmore or less even, rectangular lobed (but flat, round lobed, often scarcely lobed), distinctly convex slightly convex
Pinna-segment apex
rounded-truncate with rounded-truncate with rounded-truncate with rounded-truncate to obtuse to slightly slightly acute teeth obtuse to acute truncate with acute to acute teeth somewhat spreading slightly acute teeth teeth
narrowly oblong to narrowly triangular tapering from near base to acute tip
oblong to narrowly oblong tapering to shortly acuminate tip
oblong to lanceolate, tapering to shortly acuminate tip
more or less even, strongly rectangular somewhat lobed, lower ones rectangular lobed (but strongly developed often scarcely lobed)
more or less even, somewhat to strongly rectangular lobed
rounded-truncate to rounded-truncate to round-pointed with round-pointed with slightly obtuse to acute teeth acute spreading teeth
squarely-truncate to pointed with acute teeth often longer at the corners
oblique-truncate to sharp-pointed with acute teeth
squarely-truncate to pointed with acute teeth sometimes longer at the corners
Lowest pair of pinnamore or less same segments on each pinna length as adjacent pinna-segments, never stalked
somewhat longer slightly longer than than adjacent pinna- adjacent pinnasegments, only those segments on lowest pinnae more or less stalked
somewhat longer and wider than adjacent pinna-segments, never stalked
significantly longer than adjacent pinnasegments, usually stalked on pinnae from above midlamina downwards
somewhat longer than adjacent pinnasegments, never stalked
slightly longer than adjacent pinnasegments, usually stalked on pinnae from below midlamina downwards, but sometimes only on lowest pinnae
somewhat longer than adjacent pinnasegments, usually stalked on pinnae from about midlamina downwards
scarcely longer than adjacent pinnasegments, usually stalked on pinnae from about midlamina downwards
Lowest basiscopic pinna- smaller and less segment on lowest developed than pinnae of frond corresponding ones on pinnae immediately above, partly attached at base
usually slightly larger than corresponding ones on pinnae immediately above, more or less fully stalked
smaller than corresponding ones on pinnae immediately above, partly attached at base
usually larger and more developed than corresponding ones on pinnae immediately above, fully stalked
slightly larger and more developed than corresponding ones on pinnae immediately above, partly attached at base
slightly larger and more developed than corresponding ones on pinnae immediately above, fully stalked
significantly larger and more developed than corresponding ones on pinnae immediately above, fully stalked
somewhat larger and more developed than corresponding ones on pinnae immediately above, fully stalked
usually slightly larger than corresponding ones on pinnae immediately above, more or less fully stalked
Affinis Watch Newsletter Special Issue - April 1997
Comparative Descriptions for 'Dryopteris affinis ' complex in Britain & Ireland
Morphotype
affinis
convexa
kerryensis
cambrensis
arranensis
borreri
robusta
insolens
Pinna / pinna-segment spacing
more or less just separate
more or less separate more or less just separate
more or less distant to just separate
more or less distant
more or less distant
distant
foliose, more or less overlapping
more or less overlapping to just separate
Stipe thickness
very robust
robust
robust
robust
moderately robust to robust
slender to moderately slender robust
robust
slender to moderately robust
Scale colour
deep gold to dark gold
reddish gold
reddish gold to very dark gold
deep gold to reddish gold
ginger to reddish gold mid brown
pale straw to mid brown
gold, with dark bases light brown to dark brown, with darker base
Scale shape
narrow, twisted
narrow, twisted
narrow, twisted
narrow, somewhat twisted
somewhat narrow
somewhat narrow
somewhat wide
somewhat wide
somewhat wide
Scale density
dense
dense
dense
dense
moderately dense to dense
light
light
moderately dense to dense
light to moderately dense
Indusium shape when sporangia just ripe
tall with margins tightly enclosing the sporangia
tall with margins tightly enclosing the sporangia
tall, often small, with margins tightly enclosing the sporangia
tall, very round, with margins tightly enclosing the sporangia
somewhat tall with margins just enclosing the sporangia
somewhat low with margins just enclosing the sporangia
somewhat low and wide with margins inflected but scarcely enclosing the sporangia
somewhat low and wide with margins inflected but scarcely enclosing the sporangia and often partly flattened onto the underside of the pinna-segment
somewhat low and wide with margins inflected but scarcely enclosing the sporangia to partly flattened onto the underside of the pinna-segment
Indusium shape after dehiscence
not shrivelling but lifting slightly, often with radial splits
slight shrivelling and lifting, often with radial splits
slight shrivelling and lifting, often with radial splits
slight shrivelling and lifting, often with radial splits
shrivelling and lifting up to a clear cone, sometimes following radial splits
shrivelling and lifting up to a clear cone, not splitting
shrivelling and lifting to a small distorted cone, not splitting
shrivelling and lifting to a distorted cone, not splitting
shrivelling and lifting to a small distorted cone, not splitting
Indusium persistence
mostly remaining on over-wintered fronds
mostly remaining on over-wintered fronds
mostly remaining on over-wintered fronds
mostly remaining on over-wintered fronds
some remaining on over-wintered fronds
some remaining on over-wintered fronds
very few remaining on a few remaining on over-wintered fronds over-wintered fronds
Character
paleaceolobata
Anthony Pigott
Affinis Watch Newsletter Special Issue - April 1997
very few remaining on over-wintered fronds
Affinis WATCH necessarily be the correct names in the sense of the formal nomenclature.
when you find it, long before you have done the character analysis to prove it to yourself logically.
Some of the morphotypes need little introduction. Morphotypes affinis and cambrensis are widespread and relatively easy to identify. They are also typical and the most frequently found components of the wider ranges covered by 'subsp. affinis' and 'subsp. cambrensis'.
Not described here, but significant from the point of view of identification are the 'D. affinis' complex hybrids. There are known to be hybrids with D. filix-mas at two ploidy levels, thought to be from 'subsp. affinis' and 'subsp. borreri'. However there is no reason to doubt that all the morphotypes hybridise with D. filix-mas. There are certainly many examples in the field of individuals or small numbers of plants with morphology difficult to include within a known morphotype, but broadly intermediate with D. filix-mas. Similar hybrids may well exist with D. oreades although none has been confirmed. Of course, they would effectively be of similar origin to some of the basic morphotypes or D. filix-mas hybrids and therefore difficult to distinguish.
Morphotypes borreri, insolens and robusta between them cover the bulk of the variation usually ascribed to 'subsp. borreri'. Morphotype borreri is probably the form most commonly thought of as representing 'borreri' in the broad sense, with its neater, paler appearance and distinct 'cat's ears'. Morphotype 'insolens' is superficially similar to morphotype 'borreri' but is distinguished by its broader, less parallel sided frond, greater glossiness and darker scales. Morphotype 'robusta' is mainly distinguished by its much more foliose appearance with overlapping pinnae and pinna-segments even in small specimens and its generally more robust habit, especially obvious in large specimens. 'Subsp. robusta' as used by recent authors has usually represented morphotype robusta, although many specimens attributed to it may have been D. filix-mas hybrids or very large robust plants of other morphotypes. It is now often dropped, said to represent merely large developed plants of 'subsp. borreri'. Whilst the identity of the type specimen of 'subsp. robusta' may be so, morphotype robusta as described here is certainly not that. I have seen many examples of both very large developed morphotype borreri and small morphotype robusta; the two morphotypes are quite distinct. There are three morphotypes, paleaceo-lobata, kerryensis and convexa, that are somewhat similar to morphotype affinis in their glossiness and indusial shape. These have been included elsewhere within 'subsp. affinis'. All three differ from morphotype affinis in their more acute teeth and slightly less thick indusium. Morphotype paleaceo-lobata has distinct 'crimping' of the pinna-segments that gives it a very crisped appearance, quite different, once you know it, to the progressive curving-up of the pinna-segment tips in morphotype cambrensis. It also can have the darkest scales in the whole complex, sometimes approaching the colour of D. wallichiana and has more-or-less stalked lowest basiscopic pinnule/pinnasegments. Morphotype kerryensis has very truncate pinnasegments almost like those of morphotype borreri, usually with a distinctly 'chunky' lowest pair on each pinna. The indusia of morphotype kerryensis are particularly round (as opposed to the usual slightly oval, kidney-shape) compared to other morphotypes. Morphotype convexa is somewhat similar to morphotype paleaceo-lobata but without the 'crimping'. Its pinna-segments are quite flat and even but are very distinctly convex from the upper surface. It is also usually even more glossy than morphotype affinis. The final morphotype discussed here is arranensis. It is in many ways rather intermediate between morphotype borreri and morphotype cambrensis. It was first brought to my attention by Tony Church who has found it to be widespread on the Isle of Arran. I have since found very similar plants at scattered locations elsewhere. I suspect it may be the same thing as 'var. pseudo-complexa' whose description seems to fit it closely. I am not sure of this as . 'var. pseudo-complexa' is only reported from a few isolated places and I am not certain that I have seen it. This is probably the least well known and understood of the morphotypes described here. Apart from their detailed differences in characters, each of the morphotypes has a distinct look or 'jizz', as Clive Jermy puts it, which sets them apart from the others. When you are familiar with these plants, you just know that something is different
The tables of comparative descriptions are based on a 'spreadsheet' that I have maintained and expanded over the last few years. This was originally produced just for my own benefit in organising my ideas about the complex. There are rather more "somewhat"s, "slightly"s and "scarcely"s than I would like but I have tried to indicate the relative strength of characters even when they are not distinct enough to be useful for diagnosis. There is a need for more quantitative characters in these descriptions - hopefully that will come in time. Please remember that there are very few statements about these plants that are always true; there are often extreme forms that break the rules. These notes refer to characters of mature, fertile fronds of about 1 metre in length, growing in reasonably normal conditions (e.g., not very deep shade or very exposed). The effects of extreme environmental conditions can make significant and confusing morphological changes. This is a difficult group to understand but far from an impossible one. I have been pleased to see the way that a number of field botanists, often not fern specialists, have studied these plants and relatively quickly got to the position where they can readily recognise at least the common morphotypes and know when they have something which does not fit into the known forms. I think it is much better that we now have a number of people actively involved in observing, collecting and describing, rather than it being the preserve of a very few specialists. I have been very grateful for the support of others in studying these ferns over the years (now fifteen since I first learnt from Chris Page that there was something interesting here). Hugh Corley has been an inspiration and I am sure knows more about these plants than anyone else. Christopher Fraser-Jenkins has always been an encouragement and has been kind enough to share his views and unpublished notes with me. Occasional disagreements should not imply any lack of respect for the contribution to our understanding that he has made. Clive Jermy has been a great motivator and always provides a critical test of ideas. Very helpful field information and discussion has been provided by many including Rose Murphy, Tony Church, Arthur Chater and Ken Trewern. To conclude then, the mists are clearing in this fascinating group but there is still much to learn. I believe we must proceed in as scientific a way as possible: observing, formulating hypotheses (about the patterns of variation and the underlying genetics) and testing them (in the field, by statistical analysis and molecular experiment). Above all, we must keep an open mind and accept that we do not have all the answers. 43 Molewood Road, Hertford, Herts, SG14 3AQ e-mail:
[email protected] WWW: http://www.btinternet.com/~pigott/anthony.htm
This printing is from a reconstruction of the original into a MS Word 6 document. The original content is unchanged but there may be minor formatting differences. This version is dated Sunday 29 June, 1997: awnewsr.doc
