Highlights

Many research projects have been ﬁnished and countless papers on ostracods have been published in the time between Naples and Berlin. Among the publications, there were quite a few directing ostracodologists’ attention (and not only theirs) to the unbounded scientiﬁc possibilities that applied ostracodology may open. Some of these are: (1) a permanent reﬂection of practical ostracodology on one hand, and (2) a clear invitation to use this outstanding group of microcrustacea as a tool in applied biology and palaeontology (e.g. DeDecker and Forester, 1988; Martens and Horne 2000; Holmes and Chivas, 2002; Boomer et al., 2003).

In contrast, only a very few authors reviewed the achievements of ostracodologists in history. From the ISO proceedings, three reviews are noted which partially touched that topic. In 1976, Sohn reviewed the papers on ostracods of the previous decade, with reference to the geographical distribution of authors and to the age of ostracods being studied (Sohn, 1977). Six years later, Kesling gave an overview of ostracodology’s state-of-the-art by means of new techniques and new concepts being used for research (Kaesling, 1983). A more historical study was published by Neale (1988), summarizing the development of the most important research areas in ostracodology through the centuries. However, this overview was done in a descriptive way, mainly focusing on the achievements of single ostracod-researchers who generated outstanding results in their ﬁelds. In contrast, the present study is based on numerical data, trying to show the paths that our research actually took between 1963 and 2005, the time covered by the ISO events. Several questions are addressed: Did ostracodology react to general trends and requirements in science and/or business? How fast did new techniques ﬁnd their way into ostracodology? Which research methods are well represented in ostracodology, and which are not (yet)? On the occasion of the present proceedings volume (part 1) of ISO15, a retrospect on ﬁfteen ISO proceedings may shed a light on the recent history of ostracod research, and may even help to see where the future will take us.

Materials and methods

For the presented study, the following proceedings volumes were analyzed:

· ISO1, Naples 1963 (Puri, 1964), Ostracods as Ecological and Paleocological Indicators

· ISO2, Hull 1967 (Neale, 1969), The Taxonomy, Morphology and Ecology of Recent Ostracoda

· ISO3, Pau 1970 (Oertli, 1971), Colloquium on the Paleoecology of Ostracodes

· ISO4, Newark 1972 (Swain, 1975), Biology and Paleobiology of Ostracoda

· ISO5, Hamburg 1974 (Hartmann, 1976), Evolution of Post-Paleozoic Ostracoda

· ISO6, Saalfelden 1976 (Lofﬂer and Danielopol, 1977), Aspects of Ecology and Zoogeography of Recent and Fossil Ostracoda

· ISO7, Belgrade 1979 (Krstic, 1979), Taxonomy, Biostratigraphy and Distribution of Ostracodes

· ISO8, Houston 1982 (Maddocks, 1983), Applications of Ostracoda

· ISO9, Shizuoka 1985 (Hanai et al., 1988), Evolutionary Biology of Ostracoda

· ISO10, Aberystwyth 1988 (Whatley and Maybury, 1990), Ostracoda and Global Events

· ISO11, Warrnambool 1991 (McKenzie and Jones, 1993), Ostracoda in the Earth and Life Science

· ISO12, Prague 1994 (Riha, 1995), Ostracoda and Biostratigraphy

· ISO13, Chatham 1997 (Boomer and Lord, 1999; Holmes and Horne, 1999; Horne and Martens, 2000), Non-marine Ostracoda: Evolution and Environment; Marine Ostracoda and Global Change; Evolutionary Biology and Ecology of Ostracoda and unpublished abstract volume

· ISO14, Shizuoka 2001 (abstract volume, unpublished), Towards the new ostracodology in the
21st century, (proceedings volumes by Ikeya et al., (2005a) and Ikeya et al., (2005b) were not
evaluated)

· ISO15, Berlin 2005 (abstract volume, Kohring and Sames, 2005), Ostracodology—linking bio-and geoscience

ISO15 and ISO14 have been evaluated by their abstract volumes because of the much higher numbers of presented projects than is reﬂected by the subsequently published manuscripts in the proceedings. ISO13 has been evaluated by both the published proceedings volumes and the unpublished abstract volume of talks and posters. The proceedings volumes of ISO12 and ISO11 included poster abstracts, which were also included in the dataset. From the other ISO events, no abstract volumes were available, thus the data all rely on the published proceedings. However, these older volumes tended to contain the majority of presentations, as rejection of manuscripts only routinely started when proceedings were published as special issues of international journals.

Very few manuscripts or abstracts presented in the proceedings were not considered in the present study, such as non-ostracod papers, general reviews on ostracod research, or laudations. In total, 906 titles presented at ISO events were categorized.

The topics of all projects, presented either as abstracts or as complete publications, were evaluated and sorted with respect to their prevailing and their secondary theme or method. No differences were made between neontological and palaeontological research, e.g. ‘biodiversity’ and ‘palaeobiodiversity’ were not differentiated.

Within the eight main topics, namely taxonomy, morphology, genetics, reproduction, biodiversity, ecology, biogeography and biostratigraphy, several subcategories were formed according to the context in which (for example) a taxonomical or ecological study had been carried out. Thus, as an example, the collected data now allow a distinction between morphological studies carried out to gain new insights into phylogeny and evolution and those to relate ostracod body characters to ecological parameters of the habitat. Of course it was not always evident how to classify the projects, but, in general, every manuscript ﬁnally contained clear arguments to choose one of the eight main categories and a secondary category.

Results

All data obtained on the projects presented in the analyzed ISO proceedings and abstract books can be viewed in the Electronic supplementary material.

From these raw data, several diagrams were prepared to visualize (1) the differences in the composition of research projects presented at the different ISO events and (2) the development of ostracod research through time. Figure 1 shows an overview of the eight main categories of ostracod research presented on the International Symposia on Ostracoda, while Figs. 2–4 show some more details on the purposes of taxonomical, morphological, and ecological studies by breaking the data down into the different ﬁelds in which context these studies were executed. Finally, the development of research on ostracod taxonomy, morphology, (palaeo)biodiversity, (palaeo)ecology, (palaeo)biogeography and biostratigraphy and the relations between them are presented in Figs. 5 and 7.

Discussion

International Symposia on Ostracoda are interdisciplinary, international meetings of ostracod researchers, convened by invitation of different organizers in different countries. The basic idea is to provide a forum for presentations and discussions among all ostracod researchers. However, traveling to symposia costs money, and not all ostracod researchers can cover the costs for traveling around the world to meet their colleagues. Moreover, fellow ostracod researchers may not be able to leave their country for political reasons. As a result, the present analyses of the ISO outcomes may not fully represent ongoing ostracod research at that time. This weakness is of course a disadvantage for the present study—however, it is a much bigger hiatus in the meetings themselves, and the editors of the present proceedings look forward to the day when every ostracod researcher will be able to attend the coming international symposia on Ostracoda.

Each International Symposium on Ostracoda has had a main theme. Most of them are rather generally phrased, but some of these themes have of course inﬂuenced the composition of the presented work—a fact that can be noted for several, particularly the earlier symposia, such as ISO1 with its high ecological or ISO5 with its high morphological score. Nevertheless, in these symposia, many contributions were still not related to the given motto, as seen particularly in the poster abstracts of ISO12: while the manuscript contributions very much reﬂect the biostratigraphic bias of the given theme, the symposium abstracts included come from all possible ﬁelds. This reﬂects a selection of oral presentations conforming to the theme, followed by a publication in the proceedings volume. However, these pre-selections most likely did not inﬂuence the general trends of the development of contemporary ostracod research, but are rather seen as a mirror of the biodiversity studies would have less relevance (and respective research climate. of course, vice-versa, these ﬁelds do contribute to a reliable taxonomy).

Taxonomy is the base of all ostracod research. Without well-deﬁned alpha-taxonomy, ecological, genetical, biostratigraphical, biogeographical and biodiversity studies would have less relevance (and of course, vice versa, these fields do contribute to a reliable taxonomy).

Fig. 5 Performances of taxonomy and morphology at the different ISO events. y-axis: proportions of taxonomical and morphological contributions in percent

Fig. 6 Performances of biodiversity and (palaeo)ecology at the different ISO events. y-axis: proportions of biodiversity-related and ecological contributions in percent

However, at ISO9, ISO11 and ISO12, the percentage of taxonomic contributions seems to be balanced around 10–15% (at ISO12 quite evenly divided among fundamental and applied studies), to be followed by the complete breakdown of taxonomy at ISO13 (Fig. 6). Possibly, this effect can be explained by a change in funding policies which (at least in the European research area) largely neglected the necessity of fundamental taxonomic research. Taxonomy went out of fashion, and had to be included in other, more applied and/or fashionable, project proposals. However, countless horrifying reports from conservation biologists about extinction trends, as well as worldwide taxonomic actions (such as the Global Taxonomy Initiative, and others) seem to have set a limit to the extinction of taxonomy. taxonomy. A budding new self-conﬁdence of taxonomists is probably also reﬂected by the re-birth of ostracod taxonomy at ISO14 (22.6%) and ISO15 (18.2%), both presenting a good mixture of fundamental and applied taxonomical studies.

Fig. 7 Performances of (palaeo)biogeography and biostratigraphy at the different ISO events. y-axis: proportions of biogeographical and biostratigraphical contributions in percent

Ostracod taxonomy is traditionally built on morphology. Since hypotheses regarding evolution and phylogeny are mainly based on ostracod taxonomy, morphology also serves in these domains. Additionally, morphological knowledge of juvenile ostracods serves ontogenetic investigations as well as life-cycle-studies. Apart from a high peak at ISO5 (owing to its theme, morphology for phylogeny and evolution was highly pronounced), morphological investigations represent the more or less continuous background technique at all ISO events (Figs. 1, 5). Since environmental factors are often reﬂected by morphological traits, morphology is to a high degree an integral part of ecological studies, as shown in Fig. 3. Increasing interest in soft-part preservation in fossil ostracods has added a new aspect to the understanding of the group as a whole, and new technologies such as non-invasive methods might even give a major new impulse to this traditional research area in the near future. There is still a lot to be expected, the future is bright!

Ecology (including palaeoecology) is one of the major ﬁelds of investigation within ostracodology (Figs. 1, 6), and apart from a clear ‘depression’ at ISO5, it was always one of the main topics in ostracod symposia, if not the largest part of all ISO contributions (which was the case at 10 out of 15 ISO events). Additionally, at ISO1, ISO6 and ISO8, a high proportion of presented taxonomic studies were aimed at an improved understanding of ecological data (Fig. 2). Within the ﬁeld of (palaeo)ecology, most studies deal with the relationship between (palaeo)diversity and various environmental factors, followed by pure environmental studies and those combining (palaeo)ecology and (palaeo)biogeography (Fig. 4). At ISO7 (1979), shell chemistry was introduced as an innovative technique for the use of ostracod shells as environmental proxies (peak at ISO13), followed by isotope analyses from ISO11 (1991, peak at ISO14). At ISO15, no project on pure shell chemistry was presented—it seems as if isotope analysis has currently succeeded as the most relevant technique if deductions from ostracod shell compositions on former environmental conditions are required. Behavioral studies related to environmental factors play only a minor role.

The outstanding performance of ecological research within ostracodology is not surprising: along with wealth and high living standards in the industrial countries, the last ﬁve decades have brought severe man-made impacts on our environments. To understand the ongoing global and regional changes, ecological survey techniques had to be improved and data were increasingly processed by more and more sophisticated computing technologies. Ostracodologists made and will make use of these developments to learn more about ostracod ecology, and—vice versa—will apply this knowledge to contribute to the understanding of both past and future trends.

The study of ostracod biodiversity is rarely a stand-alone discipline. New insights into faunal assemblages of a given time and space are usually embedded within ecological, phylogenetical, biogeographical or biostratigraphical investigations. In particular the two ﬁelds ‘ecology’ and ‘biostratigraphy’ are often inextricably interwoven with faunistic analyses. Therefore, if ISO projects featured a biodiversity study within an ecological context, or a biodiversity study within a biostratigraphic context, respectively, these were categorized within the groups ‘ecology’ and ‘ biostratigraphy’.

The remaining analyzed biodiversity studies (Figs 1, 6 and data sheets) tell us two major things:

(1) biodiversity studies executed to gain new insights into ostracod evolution and phylogeny are relatively rare; (2) in contrast, a much larger proportion of biodiversity studies combine faunal analyses with biogeographical issues, particularly at ISO10, which was dedicated to Global Events. However, from ISO10 onwards, the proportion of biodiversity–biogeography studies gradually decreased from 18.2 to 0.7% at ISO15. This development is both surprising and alarming, particularly if viewed together with the main theme ‘biogeography’, which also shows a more or less continuous decrease after ISO11 (Figs. 1, 7) with a complete absence at ISO14. Is it possible that such an important facet of ostracod phylogeny and evolution is no longer explored?

Biostratigraphy is certainly the oldest applied discipline in ostracodology. Ever since the ﬁrst description of a fossil ostracod in 1813 (Cypris faba Desmarest), ostracod biostratigraphy has been a proven method for dating sediments and strata, not least in the economically important ﬁeld of hydrocarbon exploration. Biostratigraphic contributions were relatively pronounced in the ISO7 proceedings from 1979 (34.2%), reﬂecting increased exploration as a consequence of the global “energy crisis”, then gradually decreased down to 8.9% at ISO10 (Figs. 1, 7). At the occasion of ISO12, organizers may have wanted to pinpoint this negative trend by choosing the theme ‘Ostracoda and biostratigraphy’, but the following two symposia again featured only around 5% biostratigraphy within their proceedings.

However, since the oil industry has largely replaced biostratigraphy by other exploration techniques in recent decades (in order to decrease personnel costs), it now becomes obvious that biostratigraphy is still the most powerful tool for both immediate strata dating and palaeoenvironmental assessment. The new demand for well-trained micropalaeontologists meanwhile led to the establishment of popular international open short courses in applied micropalaeontology, e.g. at the University of Bonn.

This renewed interest in biostratigraphy certainly follows new requirements in the oil exploration industry. The relatively high performance of this working ﬁeld at ISO15 (11.2%) is indicative of this trend.

Of the eight main categories of ostracod research, reproduction and genetics represent the smallest groups. Molecular genetic research ﬁrst appeared at ISO11 in 1991 (Fig. 1) with two fundamental studies—surprisingly late when compared to the general development of this research ﬁeld in the rest of biology. In the present proceedings volume, genetic contributions remained below 3% of the total number (four papers or 2.8% at ISO15). There may be several reasons for this. Firstly, molecular biological studies on ostracods are restricted to few research groups only. Ostracods may not be the most ideal model organisms for such studies, because many species remain difﬁcult to culture in the lab, and their small size (amongst other reasons) makes DNA extraction less than equivocal. Secondly, molecular biologists working with ostracods often do not consider themselves ostracodologists per se, and attending ostracod conferences might not be their priority. Finally, molecular studies on any animal or plant groups are often seen as being more competitive than more classical disciplines, and therefore such papers might not be offered for publication in the symposium proceedings.

The general under-representation of reproduction biology within ostracod research (Fig. 1) is due to different reasons. Major studies on ostracod reproduction, namely on the morphological background of reproduction, were carried out before the ﬁrst ISO, mainly in the ﬁrst decades of the 20th century, by

technically brilliant microscopists like Zenker, Muller, Bauer, Lowndes (e.g. Zenker, 1854; Muller, 1889; Lowndes, 1935; Bauer, 1940). With the rise of SEM and TEM techniques in the 1960s, several potentially ground-breaking studies on ostracod giant spermatozoa were published (e.g., Gupta, 1968; Reger & Florendo, 1969; Reger, 1970; Zissler, 1966, 1970), but unfortunately they were (1) not published within an ISO proceedings volume and (2) obviously not ground-breaking enough: apart from Wingstrand’s monograph on ostracod spermatozoa (1988), they had no ‘pollinating’ effect on ostracod research. Additionally, it has to be mentioned that these studies were not carried out by ‘genuine’ ostracodologists entering the ﬁeld of spermatology, but by spermatologists, who were only temporarily interested in ostracod spermatozoa (e.g. Zissler, Reger).

Within ISO proceedings, most studies on ostracod reproduction were related to morphological aspects, followed by investigations of the effects of reproduction on population dynamics. Karyological, ecological, behavioral and biogeographical aspects of ostracod reproduction have so far played a very minor role.

However, ostracods reproduce either sexually or asexually and asexuality (parthenogenesis) is limited to certain populations or even species, but never cyclic. Furthermore, the occurrence of parthenogenesis in certain species is correlated with geographical/ climatological aspects. These biological peculiarities indeed bear a high potential for research in, for example, ostracod evolutionary ecology, palaeo-biogeography and genetics. The ongoing SexAsex EU Marie-Curie Research and Training Network on the geographic parthenogen Eucypris virens will certainly give this ﬁeld a new impulse, so that a signiﬁcant output is to be expected. Not least, the continuous improvement of affordable camera systems will provide increasing possibilities in particular to studies on ostracod reproductive behavior. Ostracod reproduction appears to be a research ﬁeld in the starting blocks.

Conclusions

Within the spectrum of ISO contributions, taxonomy generally played a minor role and was mostly presented in a combination with other research ﬁelds, i.e. as applied taxonomy. From the 1970s, the percentage of taxonomic contributions decreased until a complete breakdown in 1998. Since then, a re-birth can be noted, perhaps as a sign for a budding new self-conﬁdence in this area. Morphology may be termed the permanent background research at high level within ostracodology, implemented in literally every working ﬁeld. Along with a growing interest in soft-part preservation in fossil ostracods, it will be more and more important to have a profound knowledge of soft-part morphologies of all ostracod groups.

Ecology is one of the major ﬁelds of investigation within ostracodology, and new techniques seem to be introduced quite easily and quickly. Shell chemistry studies had their peak in 1998, but were then gradually replaced by, or combined with, isotope analyses. Behavioral studies played a minor role, whereas most ecological studies made use of biodiversity analyses to use assemblages as environmental proxies, and often include biogeographical implications. Apart from this application, biodiversity analyses mainly functioned as a tool for biostratigraphical and biogeographical projects—only very rarely were phylogenetic studies based on biodiversity analyses. Biogeography as such has not performed well recently. In spite of useful new tools like GPS and affordable database software, not the slightest growth of this ﬁeld is to be noted within the contributions of the last ISO events. In order to contribute to developments in general (palaeo)biogeographical research, work on ostracod biogeography urgently needs to be revived. In contrast, biostratigraphy seems to have overcome its low mark, which was clearly at ISO13. Ever since, renewed interest in this area is to be noticed. Molecular genetic research found its way into ostracodology rather late and after its introduction at ISO11 in 1991 no signiﬁcant ﬂourishing can be seen in the present analysis. Several possible reasons can be cited for this. Finally, research on ostracod reproduction has had its special chronology. The main morphological data on reproductive organs and cells were collected by researchers before the ﬁrst ISO in 1963. Among the ISO contributions, the percentage of studies on reproduction were generally low, featuring morphological peculiarities, a few chromosome investigations, sex-ratio studies and only one manuscript (in total) in either an ecological or a biogeographical context. All spermatology research of the 1970s was performed by non-ostracodologists outside any ISO event. Since ostracod (a)sexuality is extraordinary for several reasons and even challenges evolutionary hypotheses by featuring putative ancient asexuals, this research area is expected to continue to ﬂourish in the future.

Although the present study suffers from a number of shortcomings (cited above), we consider this retrospective of some value, because it might help us to decide which directions to take in our coming research projects in the 21st century.

Gemeine Kopfe lesen in der Geschichte die Vergangenheit, kluge die Zukunft—Simple minds read the past in history, clever minds read the future.

Acknowledgements

We wish to thank all people who organized previous International Symposia on Ostracods, and who put a lot of work into the Symposia Proceedings. We also wish to thank all authors who published in previous ISO Proceedings, thus providing an overview on the current state of the art of ostracodology.

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