DISTANCE METHODS: A REPLY TO FARRIS

Abstract— Farris (1985) claimed that my assertions about unbiasedness and consistency of estimates of a phylogeny obtained by least squares fitting are in error. The counterexample he constructed violates the assumptions of additivity and independence of distances which were clearly stated in my earlier paper. As such it is not a valid counterexample. It is argued, contrary to Farris's claims, that one need not avoid nonmetric distances, and that one should avoid negative branch lengths in estimates of phylogenies from distance data. Statistical tests of clockness, and, to a limited extent, of alternative phylogenies can be constructed, and these are demonstrated by example. A computer program to infer phylogenies from distance matrices has been in free distribution by me for several years; it seems as effective as the program recently announced by Farris. Information on phylogenies is present in distance data, as in other kinds of data, and statistical methods can be developed to extract it.     

Gene regulation of shell banding in a land snail from Israel

The Israeli land snail, Xeropicta vestalis, offers a particularly clear example of gene regulation in relation to natural selection, in that within each population the appropriate phenotype is generated only at the correct part of the animals life cycle, and a contrasting phenotype develops when the forces of natural selection change. In the mountains of Jerusalem, where the winter is cold, the shells are dark. Westwards, towards the coastal plain where the winter is warmer, the shells gradually become paler. As dark shells absorb more radiation than pale ones, this clinal variation in morph frequencies can be explained in thermal terms. (Banded shells are also more cryptic than non-banded shells, so that in the mountains visual selection by predators may be an additional force which favours dark shells.) Xeropicta vestalis is an annual, semelparous species: the snails hatch in winter, become mature within one year, reproduce, and then die. In the coastal plain the snails are active throughout most of the year, and they have a long period in which to grow to reach adult size. In the mountains and hills, on the other hand, the snails are active for only a very short period. They spend most of their lives as small snails, in a state of aestivation. Xeropicta vestalis must be dark in mountains because when it finally awakens, it must very rapidly and hastily reach reproduction size. A dark shell, by speeding up temperature-dependent processes in this critical stage, assists the snail to mature rapidly. Shell darkness varies with age: in the mountains and hills the shells are moderately dark when they hatch, but become darker whilst growing in early winter. In the coastal plain also, the snails are moderately dark when they hatch; but here they become paler, whilst growing in winter and spring. In both cases, each snail is darker in the colder months and paler in the hot ones. A strategy of gene regulation of shell colour is thus favoured when the subsequent forces of the environment are very contrasting in their direction, very severe—yet also very predictable.     

Resistance of Calves to Reinfection with Eimeria bovis

SYNOPSIS. An immunity to reinfection with E. bovis was demonstrated in 3 experiments involving 60 calves. This immunity develops rapidly, as indicated by resistance to a challenge given 14 days after the immunizing inoculation. In 3 groups of 3 to 6 young calves each, immunity was still present to a moderate degree 2 to 3 months after inoculation; in one group of 5 animals about a year old there was apparently a high degree of immunity about 7 months after the last inoculation. In one experiment an immunizing inoculum of 10,000 oöcysts did not produce as much immunity as 50,000 oöcysts. In 2 experiments there appeared to be little difference in the immunity produced by a single inoculation of 50,000 as compared with 100,000 oöcysts, but inoculation with 100,000 oöcysts, resulted in substantially longer and more severe illness than 50,000 oöcysts. There appeared to be no appreciable difference in clinical symptoms or development of immunity between calves given a single immunizing inoculum and those given the same number of oöcysts in 5 equal inocula on successive days. Treatment with sulfamethazine and sulfamerazine (Merameth) 13 to 15 days after inoculation alleviated the clinical symptoms of coccidiosis without interfering appreciably with the development of immunity. In one experiment with 7 calves, no beneficial effect was noted from 1 or 2 transfusions of 500 ml. of plasma and leucocytes from immune calves into 4 calves 1 and 12 days or 11 days after a challenge inoculation.     

METHODS FOR THE STUDY OF BLOWFLY POPULATIONS

The advantages and disadvantages of laboratory-bred material for fly-marking experiments are discussed. Experimental evidence suggests that the tendency to uniformity of history of laboratory-bred blowflies in relation to protein-feeding produces no rhythm, apparent in the first 4 days at least, in their response to protein bait attractants.
The change from insectary environment to field conditions may sometimes result in either a greater or a lower proportionate recapture of a laboratory-bred sample than that for a comparable wild-caught sample. The nature of the difference is apparently associated with the weather conditions of the release area, but may be due to other causes, probably including physiological debilitation of laboratory-maintained strains.     

EVOLUTIONARY TRENDS IN FROGS

Fossil evidence concerning the Anura adds guide-lines to phylogeneticinterpretations, but in large part evolutionary informationhas come from comparative studies of moderns. Trends withinthe Anura, established in different lines, provide an importantsource of clues for major phylogenetic interpretations. A numberof such trends, both osteological and non-skeletal, are analyzedand their phylogenetic implications assessed. Two major lines of development are postulated. One branch includesthe notobatrachid-ascaphid and the pipid-rhinophynid sublines.The other major branch includes the advanced frogs with procoelouscentra. The advanced frogs were derived from a primitive stockprior to the development of anything that would be recognizedas a notobatrachid-ascaphid-opisthocoelan line, rather thanfrom such a line.     

Variation in the Competence of Tobacco Pith Cells for Cytokinin-Habituation in Culture

Pith parenchyma tissues of tobacco sometimes lose their exogenous requirement for a cell division factor such as the cytokinin, kinetin. This process, known as cytokinin habituation, appears to involve epigenetic changes since it is a heritable change in cell phenotype which is directed, regularly reversible, and leaves the cell totipotent. In this report, we show that pith cells in culture consist of at least two types of cytokinin-requiring cells. The first type habituates rapidly under inductive conditions. The second type continues to express the cytokinin-requiring phenotype for many cell generations in culture but retains the capacity for habituation. These findings suggest that pith cells differ in their competence to habituate and that different states of competence are inherited by individual cells.     

Phylogenetic relationships among marsupial frog genera (Anura: Hylidae: Hemiphractinae) based on evidence from morphology and natural history

We reassess the phylogenetic relationships of genera of hemiphractine hylid frogs (Marsupial Treefrogs) and discuss the evolution of several distinctive characters within this group using parsimony analysis. Fifty-one morphological and life-history characters were sampled from two species of Cryptobatrachus , three species of Flectonotus , 17 species of Gastrotheca , all five species of Hemiphractus , and one species of Stefania as the ingroup and three hyline, one phyllomedusine, and one pelodryadine species as outgroups. Our results support the mon-ophyly of Flectonotus, Cryptobatrachus , and Hemiphractus. Gastrotheca is paraphyletic with respect to Hemiphractus , dorsal pouches were lost in the ancestor of Hemiphractus. Direct development is a synapomorphy for Hemiphractinae and tadpoles were regained independently several times. These results stand in stark contrast to the prevailing paradigm regarding marsupial frog relationships.