Verifying Abies at Bedgebury Pinetum

Bedgebury Pinetum, as a collection of around 10,000 specimens, will inevitably contain some wrongly labelled or mis-identified specimens. Reasons for this will vary – for example, initial mis- identification in the field when the were collected or seeds and labels getting mixed up. In most cases, while these errors may not be apparent to the public, they will have important implications for science and conservation. For instance, when specimens are required from Bedgebury for research or analysis, as they were when testing for susceptibility to the pathogen Neonectria this year, it is imperative that they are correctly identified so as not to result in erroneous conclusions. Furthermore, close morphological examination of specimens in cultivation have in the past yielded the discovery of new species, for instance A. chengii (Rushforth, 1984), and A. pseudochensiensis (Debreczy, 2010).

However, correct identification requires close detailed study of the morphology (external characters) and, sometimes, anatomy (internal structures) of these . Thus, thanks to generous grants from the Stanley Smith Horticultural Trust and the Friends of Bedgebury Pinetum, I was employed with the aim of verifying some of the in the Pinetum.

I made a start on this project with the genus Abies, or silver . This genus comprises a group of around 40 species (Eckenwalder, 2009) found across the northern hemisphere. It is highly complex in terms of with many intermediate forms, hybrids between species, and local ecotypes

The charateristic needles of Abies numidica, a rare from

(Dörken & Nimsch, 2018) . At Bedgebury there are 590 specimens of Abies, only a small number of which have been formally verified. The process of verifying specimens involves analysing basic macromorphology, e.g. length, apices, crown form and cone character, which in distinct species, such as A. cephalonica, can be sufficient data to verify the species with a high degree of certainty. However, in some, such as A. nordmanniana ssp. nordmanniana, A. nordmanniana ssp. equi-trojani and A. bormuelleriana (the precise taxonomic status of which is disputed), I had to take samples to analyse in more detail.

A recent monograph on the morphology of Abies (Dörken & Nimsch, 2018) inspired me to take my morphological observations to the microscopic level, counting stomatal density, and observing leaf cross sections and anatomy such as resin canals. An inevitable find was that, as with all aspects of morphology, micromorphology varies considerably, and while it can help inform a conclusion, it is by no means diagnostic, as shown in the graph below.

70

60

50

40 A.nordmanniana ssp.

30 nordmanniana Frequency A.nordmanniana ssp. 20 equi-trojani

10

0 4 5 6 7 8 9 10 11 12 13 Number of lines of stomates per band

A graph showing the frequencies of the numbers of stomatal lines on the undersides of 80 of the two subspecies of . Note the high degree of overlap.

Identifying a specimen involves comparing the range of features available with those most consistently associated with the type. I tried to maintain as holistic a concept of the species as possible, not focusing exclusively on reproductive features which, although frequently emphasised in taxonomic works, are often not available. Although I had previously given considerable time to the study of many different members of the genus, verifying them proved a very challenging task; in the silver firs many of the “diagnostic” features are highly variable with respect to the age of the and crown position, and many species have overlapping characters. Studying the discrete morphological features of some groups with more disparate species and non–overlapping ranges, such as many Tsuga, tends to result in one having a more typological species concept. In contrast many species of Abies e.g. the Turkish firs, represent, to some extent, a morphological continuum.

As well as considering the morphology at a given moment in time, one can also study how it changes with response to environmental cues (phenology) such as seasonal changes, for example when buds burst. I have only recently become interested in using phenology and aspects of development (ontogeny) for the identification of species. The most recent species to be discovered, or rather reclassified, Tsuga ulleungensis, was done so partly as a result of such phenological differences (Holman, et al., 2017). After analysing the specimen, I assigned a taxon name to it, and input this in IRIS, the database used to store information on all specimens at Bedgebury, along with a description to justify the choice. This ensures that all descriptions and observations will be available for further study.

In this way I was able to verify over 100 trees in the first few weeks of the project. One of the most challenging was a specimen labelled as a Grecian fir, A. cephalonica (shown below). It has short, thick, obtuse needles, with strongly included bracts (unlike the longer, mucronate needles and exserted bracts found in the type) and an A.cephalonica×A.nordmanniana hybrid . Both will require further work, phenological data, or an expert opinion to verify with high certainty.

Abies cephalonica?

With a large number of Abies specimens still to be verified, I look forward to continuing this project as soon as circumstances allow.

References Debreczy, Z. &. R. I., 2010. Abies pseudochensiensis — A new fir described from cultivation from European living collections. Acta Botanica Hungarica, 52(3-4), pp. 305-313.

Dörken, V. M. & Nimsch, H., 2018. A monograph of leaf characters in the genus Abies (Abietoideae, ). Remagen-Oberwinter: Verlag Kessel.

Eckenwalder, J. E., 2009. of the world : the complete reference. Portland: Timber Press .

Holman, G. et al., 2017. A New Species and Introgression in Eastern Asian Hemlocks (Pinaceae: Tsuga). Systematic Botany, 42(4), pp. 733-746.

Rushforth, K., 1984. Abies chengii, a previously overlooked Chinese silver fir. Notes Roy. Bot. Gard. Edin., 41(2), pp. 333-338.