Modes of evolution mainly among marine invertebrates An observational approach by H.J. Mac Gillavry Geological Institute of the University of Amsterdam Rapid advances, mainly in macro-molecular biology, eluding ecological genetics) and from mathematical make it models based such information. necessary to return periodically to the sum on It is common- total of observational information and to rebuild place, but only partially correct, to say that genetic is limited of intra- theory on evolution from the ground up. The possi- information largely to a study bility of incorporation of genetic informationby viral specific variation and to the intra-specific evolution the non-deleterious nature of of local insular term local here includes infection, many point- or races (the mutations (which follows from phylogenetic estimates the laboratory environments). Views on evolution based distances the limit is on minimum mutation in specific beyond species (whatever meant by this), derived obtained detour proteins), and the relevance of the genetic environ- as from genetics, are by a ment to mutation (obvious from physico-chemical through theoretical and mathematical models >). An- but few of the data which other less that considerations), are a new point, frequently made, is most genetic from of may be mentioned. Less obvious, but equally neces- information is obtained the study non-marine animals and and of sary is a reappraisal of paleontologie information. An plants, nowadays equally non- this field the marine bacteria and virus. Macro-molecular important gain in is greater accessibility biology, the wealth thanks the form of of immense of facts mainly to the new genetics, is rapidly beginning to efforts of Invertebrate Pale- contribute the of evolution far R. C. Moore (Treatise on to problem over The contributions of ontology), J. Piveteau (Traité de Paléontologie), and greater taxonomie distances. of for this level of inferen- L. Hyman the recent fauna (The Invertebrates). paleontology at are necessity This will deal with information tial. paper paleontologie obtained first from personal observation and secondly The observation of evolutionary phenomena and from literature. successions, on the other hand, is by its nature the Discussions evolution should make clear dis- field of of there is on a study paleontologists. Again some between: the mechanism of vertebrates. This for tinction a) evolution, b) emphasis on is understandable, observed evolutionary phenomena and successions, the vertebrates are possibly the only phylum which and the over-all of c) panorama of faunal and floral presents an intelligible succession classes, com- evolution. plete even with a number of intermediate links. In of the over-all is the second skulls and skeletons, their Appraisal panorama represented place by very for far of instance by the visionary works of Teilhard de complexity, are more expressive evolutionary Chardin for critical than in other words (see SIMPSON, 1960a, a review). change e.g., Foraminifera; they take The emphasis is on evolution towards man, and not provide a wealth of features that one can hold towards orchids mammals and other of. the other hand or octopi; verte- On they are more rigidly inte- brates profit by reflection. Speculation in this field, grated functionally, in particular under the strict whether obtained revelation terrestrial and thus have less by or otherwise, is requirements of life, bound to be rather and should be tolerance for evolution 2 airy, in any case non-adaptive variation or ). based integrated with a thorough understanding of the two Most paleontologie information is on a com- other still far removed from such of material derived from scattered aspects. We are parison museum understanding. localities, and the arrangement of this material in Ideas the mechanism of on evolution stem largely supposed phylogenetic lineages. A more rigid study from information classical based supplied by genetics (in- on sampling continuous sections, continuously Downloaded from Brill.com09/29/2021 04:28:25PM via free access 70 H. J. MAC GILLAVRY fossiliferous and with non-varying lithologie facies the field of genetics of Foraminifera is still complete- is required. Such rigid temporal control is not easy ly virgin. A useful compendium of many observed limited Foraminifera to obtain. Common situations are: a) a num- cases of evolutionary change among is ber of fossiliferous beds is separated by barren inter- provided by the Van der Vlerk jubilee volume (Vox drawback vals; b) a section, though continuously fossiliferous, Koenigswald e.a. ed., 1963). A of the shows of facies that is lack of will be in the many changes or assemblage, so group expression: it difficult, single species or lineages are not found in uninter- case of fossil forms, to find forty characters, the of minimum for methods. rupted sequence; finally the possibility immigra- required some multivariate tion and related forms should be The from studies of well- replacement by kept impressions acquired my in mind. Such studies have so far been few; well sections are: Brinkmann's studies known examples are of Kosmo- a. The great majority of species do not show any ceratidae and Trueman's studies of Gryphaea. The appreciable evolutionary change at all. These species fact that Trueman's results have recently been ques- appear in the section (first occurrence) without ob- demonstrates then should in stable tioned that even one pro- vious ancestor underlying beds, are once ceed with 3 material that the and without caution ). It is on such established, disappear higher up leaving of numerical will be of obvious descendants. Such 6 use taxonomy great phylo- any "relay expansion" ) for the market genetic importance. What, to my knowledge, is com- is typical open of neritic (sublittoral) of the benthos. pletely lacking, is a quantitative study entire fauna of such successions. A study of this kind should b. One or two species vary rather wildly without attention the of forms which do have little of this pay to percentage any time-sense. I experience type; not show it to be rather any evolutionary change. appears common among Liassic Lage- forms During my work as an oil paleontologist I had the nidae, although this family also contains some opportunity to study sections meeting these rigid exhibiting sustained change (BARNARD, 1963). Notable marl formation of East the requirements (the Tertiary recent examples among Gastropoda are species Java, for instance). As an ardent student of evolu- of Neritina where one can hardly find two specimens the watch for with the The of these tion, moreover, I was continually on same pattern. genetics species evidence of evolutionary change. The first conclusion should be exceedingly interesting; I do not know work has done this 7 to emerge was that such .instances are hard to find, whether any been on problem ). and that do not show after many species any evolutionary c. One species, a diligent search, was thought all. It be contended that more de- show a sustained This a small Tritaxia change at may a to change. is tailed and quantitative examination, for which there in the Miocene of South Sumatra, which changes commercial would have disclosed from triserial biserial uniserial the is no time in work, through to in more but such an should not be adult. However, was found that in the end it many cases, opinion it belief triserial form. based on a mere founded only on theoretical reverts to its original considerations. limited d. few forms show My studies were to Foramini- Only a really sustained change. benthonic and to lesser extent This be either fera, mainly forms, a may change along divergent lines, as of to Ostracoda. Foraminifera are of particular interest in the case of Bolivinoides (HILTERMANN, 1963) because forms have with which have the many a life-cycle alternating I no personal experience, or change a adult which is be directional, often with generations: diplont generation, may parallel development often adult branches. This is the rare, gives rise by embryogenesis to an along independent in particular which is the more fre- Foraminifera GILLAVRY, haplont generation normally case among larger (MAC quent by far, and which by gametogenesis gives rise 1963). The evolution of these forms is composed of 4 at first to zygotes from which again grow diplont adults ). the successive introduction of new features, The have the have in saltative diplonts many nuclei; haplonts part of a population (non-directional, only one nucleus up to the moment of gametogenesis. change) and the elaboration of the morphologic con- The therefore reduc- group provides a unique genetical sequences of these new features by nepionic situation animals: selection be relaxed in tion The is therefore among may (directional). parallelism com- the in the far and of non-directional introduction non-numerous diplont generation; more posite consists a the other of features direc- frequent haplont generation, on hand, any of the same succession new plus selective unless small bal- tional elaboration reduction advantage, extremely or by nepionic (acceleration, be anced by other factors, could lead to complete ex- tachygenesis); divergent changes may superposed clusion unfavourable situa- this. directional in- of variants, leading to a upon The component occurs tion without further selection 5 As far I of the the entire ). as know, dependently in lineages same genus; Downloaded from Brill.com09/29/2021 04:28:25PM via free access MODES OF EVOLUTION MAINLY AMONG MARINE INVERTEBRATES 71 faunae complex may take place in the same, though not Foraminifera among the Tertiary well-sample dif- of Indonesia. also that such forms necessarily anatomically homologous manner, in It is likely consti- ferent families. tute the bulk of the material studied by geneticists. observations with other What the Integrating these aspects is studied, however, is established form, of three main hence the These have not lost evolution, one may roughly distinguish term wild-type.