Ghosts of Competition and Predation Past: Why Ecologists Value Negative Over Positive Interactions

Abstract

In this lake, where competitions are fierce and continuous beyond any parallel in the worst periods of human history; […]; where robbery and murder and the deadly tyranny of strength over weakness are the unvarying rule; where what we call wrong-doing is always triumphant, and what we call goodness would be immediately fatal to its possessor, – even here, out of these hard conditions, an order has been evolved which is the best conceivable without a total change in the conditions themselves; an equilibrium has been reached and is steadily maintained that actually accomplishes for all the parties involved the greatest good which the circumstances will at all permit. In a system where life is the universal good, but the destruction of life the well nigh universal occupation, an order has spontaneously risen which constantly tends to maintain life at the highest limit, – a limit far higher, in fact, with respect to both quality and quantity, than would be possible in the absence of this destructive conflict. (Forbes 1887:87.) Phenomena in ecology are diverse. One would expect diverse phenomena to be investigated from diverse theoretical perspectives, but there are only a few dominant perspectives in modern ecology. Both negative and positive interactions occur in nature, and the importance and impact of both vary in time and space. It is not true, for instance, that competition and predation are the major forces affecting the fates of all communities and populations (cf. Hairston 1989). Nevertheless, ecologists have shown more interest in negative than in positive interactions. Let us consider how diverse phenomena have been explained in terms of competition or predation. Examples include the diversity and structure of communities (Paine 1966, Diamond 1975, Menge and Sutherland 1976), latitudinal gradients in body size (McNab 1971), the evolution of body size (Dawkins and Krebs 1979), the latitudinal diversity gradient (Dobzhansky 1950, Menge and Sutherland 1976), the diversity–stability rule (Lehman and Tilman 2000), trait evolution (Brown and Wilson 1956), and many phenomena about insular or isolated populations and communities (Grant 1966, Lomolino 1985). There is no list of phenomena explained in terms of positive interactions that is close in diversity to those ecologists have explained in terms of negative interactions. Positive interactions refer to cooperation (+/+), symbiosis (+/+) or (+/0), mutualism (+/+), and commensalism (+/0), in which at least one participant (an organism, population, or species) receives positive effects from the interaction without negatively affecting the other participant. In the case of negative or antagonistic interactions such as competition (−/−) or predation (+/−), at least one participant negatively affects the other. I conducted a preliminary analysis by searching for the hits of six common interaction terms from articles published in journals (n = 11). The terms in question were the same as those given below. I used the publisher's web pages, if available, or JSTOR (searching titles, abstract, and keywords for all available years). Table 1 and the graphic depiction in Fig. 1 report the data: Across different journals, competition and predation dominate in terms of numbers of published articles making reference to them vis-à-vis positive interactions. Aggregate data on numbers of hits for search terms in journals, as shown in Table 1, are not informative about dominance and its reasons. It reveals nothing about the relative frequencies of the search terms as research topics. It is also silent on the issue of whether the dominance has changed over time. Data were collected from five journals via JSTOR. I searched for hits for the following six interaction terms from articles published in journals: “competition,” “predation,” “cooperation,” “symbiosis,” “mutualism,” and “commensalism.” The dataset contains more than 50,000 published articles searched for the above six search terms, covering a period of publication history ranging from 60 to 100 years. I chose a 10-year period as the interval for the collection and comparison of data. The search covered the abstracts, titles, and key words of all the articles published in the journal in question. These data were collected and recorded as hits for each search term, and in other words, the number of articles published in the journal within a certain period that made explicit reference to a search term. The resulting data are recorded in Tables 2–6 for each journal. Given that the number of articles published in journals varies over time, the number of hits for a search term in a specific journal during a certain period (data in Tables 2–6) does not in itself give the right sort of information about its relative prevalence, currently or previously, in that journal. The numbers of articles making reference to search terms were converted into estimations of relative frequencies (i.e., the number articles that count as hits for the search term/the number of all published articles in the journal). These relative frequencies, expressed as percentages, are recorded in Tables 2–6. The reason for making this conversion was to obtain dimensionless numbers that could be compared, which facilitated comparison of the relative importance or centrality of search terms qua research topics in different journals and different periods. The requirements for a journal to be counted as a data source included having a relative long history of data available online (at least from the year 1950), most of the articles being in English, and allowing estimation of the number of all published articles within a certain period for the whole period under investigation. Quite a few journals fulfilled these requirements, including those listed in Table 1, such as Plant Ecology. Two journals that are in and that are more specific were as data The of and as the journals to the that the is published by an and the by a and ecology the data are a in was Plant The in the at least during the was on the ecology of Two journals, the of and the of and one the of were as The data could be both these journals and to data from the and journals have long publication I give reason for journals in and ecology in the all the interaction terms were included in the as I to on the most and were for the search terms is the most only is an term that could specific positive is that not all the hits in the refer to cooperation as a Table and the the numbers of hits could be The is of The term does not all of the and the number of hits could be Table and the is term, which I included positive interactions. There is a close symbiosis and certain include and even predation under interactions and as to its that interactions in are the relative frequencies of the search terms, was to the total number of articles published in journals during each period included in the There is no for these from all the journal would be and as to as was possible to obtain these data online for all the periods under and I used other In certain I chose a year that the number of numbers over a counted the number of articles published that and that number by In certain other was to count the number of articles from a certain year as of or to to count the number of articles published in year as of other during that period to that number and to the In the there was in the journals in terms of and In certain journals, the number of published articles issue a during the time the was more in In fact, in there was a an in numbers in the articles are the total numbers of articles published in a journal during a 10-year period are estimations and are in the of Tables 2–6. I have or that an or would all the on these estimations within that that in Tables 2–6. or of the total number of articles would the The the on an or the the is from the The in the percentages, or by is and for the highest and and for the under below. I investigated journals to and Given that the data to the terms searched in different journals and different I there are as far as estimation is of the I are on data from different Nevertheless, the are on the in Tables 2–6 be of than and The numbers of hits for the search terms and 2–6) within a given period in a journal are not One could count as a for any number of search It was beyond the of the to any for certain search terms to occur even the data that many articles reference to both competition and predation. The data collected how competition and predation have ecology. The numbers and of published articles to negative interactions the or these and of all articles published in journals made reference to competition the numbers for positive interactions were the have competition and predation dominate vis-à-vis positive interaction in terms of numbers and The not be as that the for competition and predation are of the or It is that many of the articles that count as hits are or no data to these the is where the research and in ecology have and what are The is that there has been in ecology negative over positive interactions in published and there a at the reveals that even if a search term the highest number of hits during one of the investigated periods in a does not that the relative was the highest during that the highest number of hits in the period of for each the relative to Let us Table The highest number of hits for competition in and the total number of published articles in the journal from to the number of articles to competition (i.e., also the number of articles to competition in terms from to It is the relative of search terms than the numbers of hits that is the most Data on numbers of hits give information about the relative or importance of search terms qua research topics. The for competition are and the of Tables Table and the of Table and for predation are Table the of Table and Table The for positive interactions are these interactions dominate which the data from Tables is in the of with for both predation and competition and for positive interactions Fig. The are in Fig. Fig. and the of with for competition in certain periods and for predation Fig. and for competition during certain periods in the of Fig. competition or predation dominate the investigated periods in both the numbers of published articles and The data an of The not always the of articles making reference to competition and predation to in the or in all the journals the of which have been a There was an in hits for competition and predation in all the journals from the or and in the or the have in the highest for competition was in the and in the period the numbers for predation are and The is but in other journals: and in for and and for predation It is possible that the same is in the of Given that no data were available for the was not possible to whether the hits for competition and predation on or Nevertheless, the for competition in the of is the highest for predation The highest for positive interactions far those for negative the highest being for cooperation and in Table The numbers and could be in this case and in instance, and hits in the of These numbers to be the I out that nothing to with cooperation as a these were and the numbers were and In this the for cooperation would have been and The are in both The highest for positive interactions are for in in and in the of to symbiosis the highest are in the of in and the of and in has been a investigated with a highest of Table In is in than of all articles published in the The numbers are given that commensalism could be the rule than the in ecologists that negative interactions are and more than other give structure to communities for The was and for instance, in the of for the is Hairston 1989). if the of negative interactions structure to communities was true, interactions major in and communities and the by There are no to interactions in or effects than other interactions. The for positive interactions from that for negative interactions. Both the numbers of articles making reference to and the for positive interactions are currently in the journals more in than in the least in this but at least in journals there is a Fig. the numbers in vary to symbiosis and mutualism there is a in all the journals with the of the of with to is commensalism Fig. which I will from from this The hits for positive interactions numbers of articles making reference to to have in the or in a journal that to be most negative the of in which there is the least for competition and predation as well to for competition and from to for the positive interactions are on the in terms of both numbers and of published articles Fig. The only is the of in which there has been a for both negative and positive interactions The period of publication history in the journals There is no period in which at was not In journals, both competition and predation are dominant in is competition There are The the dominance of could be an to the The a dominance of competition predation in the journals, is and of the for the dominance of negative interactions. In from to Fig. the for cooperation are than those for predation. in the of cooperation competition on and predation the Fig. could be a of the The hits for could be explained and the hits for be in both for the there are no hits for for the in for instance, the that the was a in the articles published during the period It be that the term in and I will to with reference to all the journals and even if in a of the in the published It is that even if the numbers and for are and the numbers and for are the is and predation dominate in ecology more than data The as the for both competition and predation in the of the or Fig. interactions were not dominant in the journal this In fact, are dominant in this journal than in any other there is no dominance of predation in this journal. I that this is an the period is and the is the for positive interactions are not The is in the of is not as Fig. to the are the or the for predation also There is a the journals and the the of in which the for competition and predation are and those for positive interactions are there to be in the dominance of negative It is more in certain journals than in It is that the reason for the dominance of in (cf. are by and to diverse good and are and and These which many ecologists also of as or could for the dominance of competition and predation is a to of a could be a for different reasons. I there is in competition or predation to be in terms of the of one or of the in a competition or predation and the is a for mutualism or to most of as as the In fact, of negative interactions have more over time. one about the conditions under which competition for instance, not in and more and more conditions and are to these if were the case that competition and predation were than is not a of a be In ecology has a in making (cf. The above for competition and predation as of the is The as the case that the of what competition be was a diversity of with in a in which are and competition was not the to on the of ecologists the case as a the data have the the reason for its was that was as It is that there are more data on competition and predation than on positive interactions. The of data no for the In the this could be the of dominance than the is not that data these as more and more has is whether these are by data than It is for instance, that the of articles as hits for competition and predation in dataset out to that were of or even data these is that competition and predation data about phenomena than the has phenomena that competition have been used to for could well be explained by that have nothing with competition (cf. and In other words, the same data and predation to be having been to diverse many phenomena within a few theoretical and are not and be and the and of competition and predation is In the case of phenomena given as in the was on that many of the from such were not and other were to at or more is possible that the of competition and predation in and diverse phenomena is the of theoretical dominance in the than the The above not be as of competition or predation there is of them in this is the following These dominate there being for the dominance vis-à-vis if this is true, the I will a and be to is that competition and predation have in ecology at least of the of in the this one would data about the history of ecology and on the and fates of ecologists in the In what I on data collected by which ecologists in the I was to data from this I on and that are (cf. no major in the research topics in terms of data or and journals for the the be those a in ecology or a during a were in certain in the The numbers and during the and of the the the numbers of with a and other to was not the that there was of the of under years. of the were a the were not given research a few with a or any other or research to over of the of modern most of those published articles and as were I the in articles published in a could be as a in as to and in 1950, there were as to I the numbers in of articles were by at least one a there are no data on the of on the web of journals, of or JSTOR for the all periods certain more or Plant ecology and are with a of (cf. Table 1 in the is of ecology. It has also been that are different (cf. and for a It is that and dominant and theoretical and such as and and and and theoretical that into different and interactions. there is one in which negative interactions dominate as is the of One of the most ecologists was that of not be explained in terms of negative interactions. and to and interactions as for the of is an case in that a the of what be in an which is in with the of in research on and and are not with this but that the in were to and or as and as well also in and in which competition and as the that other such as cooperation could well the data. case in or at least the dominance of negative is by The of by the of by the of and the of and in the of for instance, were in the but was these interactions were with mutualism and commensalism by certain in the published on symbiosis there was a to these phenomena in terms of negative The this included on of Both were reason ecologists would be in negative interactions was to and topics that on the more and and of was the of the and which also the for the and interactions that are in this were as be that the of negative interactions for was a more for the of from the and The and the many of are of to the in were and that to negative interactions. ecologists the and of and of and of and on is that the of these by occupation, negative interactions. interactions with these and have and other and of this on the research of ecologists in the case is the research by for In the is on negative interactions The is that there to be a in the research on research negative interactions as in there to be in the The term research the and above that the negative interactions. the data in the the following if is there be journals that are more or of time. In other words, the dominance of competition and predation be more in certain journals than in the of dominance in ecology be the of the in the of competition and predation as more ecology qua The data and in the these The of is by competition and predation The in dominance is least in this as is to be if the is as Both of the journals, the of and the of are by competition and predation than the of (cf. or any other journal investigated In fact, the data the possible dominance of cooperation over competition and predation in these journals are The in the dominance of the which in the or and is in all the journals to with the in the numbers of as in ecology. the in terms in numbers of for positive interactions in journals which in the or the that more and more the of ecology and as data in the of not at least predation was dominant in this journal and and there is also a hits for positive as if more the the for competition and predation have risen and in the case of competition I the journal be a There is also an I the data I that the of on competition in the and that there was currently a I the and for with this information The for competition could be to and I could the data as and not affecting the does have an on and journal It is that data from other journals of ecology also the dominance of competition 1, Fig. There is a in these journals, as in to to of I that this was the case I collected and I a journal as an data source and a to ecology for this were is not and have been research in for at least a than in ecology The into the following There be in to to about what be dominant in which for and as data are the is in on competition and predation and more on positive interactions in journals vis-à-vis ecology the data The for competition and predation in the of during all the periods covered are the of all the investigated journals the for positive interactions are not for these in a journal One well if a ecology and a journal could or be are in other topics the ecology of such as and both the number of articles making reference to interaction terms and the be even if the numbers were the be the number of other topics in is higher, which the interaction an for the for competition and predation in the It from the of interaction terms in this these data no that there is to to of theoretical dominance in than in that is a of the history of to research in the of It is that the numbers and in the of and the of be and that the of not the for competition and predation in the of The number of articles making reference to negative interactions is in the of but the is of positive more articles reference to positive interactions in the of than in the of with the of the for predation in both during the no In terms of the are The that even in the of there is a competition and there is in the of articles on positive interactions are published in a journal than in an ecology The numbers are also The of for both competition and with the of for competition There are more for in the of and more for in the of but no the for to commensalism is a for the of Ecology. The be are for positive interactions in the journal than in the ecology journal. Both the numbers and the the that competition and predation are dominant and that there is more on positive interactions in the journal than in any of the journals including the of Ecology. The is not a of the The numbers of articles to positive interactions and the are in the journal than in the the numbers and for negative interactions are if the be compared, could an of what ecology have been in the and how be negative interactions and a research not was that the research be more to negative interactions than the research There were (cf. These were to for given the of a in I also that a of have to the dominance than being the only of In fact, there to be a negative interactions in the in Table the data search was to that in the There are of or in have on negative interactions. to a in terms of how and positive interactions as the for this to and in the for with this of data is that is not how to there have been no on the of have on the dominance of that competition is for than reasons. The is that one could from by that competition is a and are that and competition and source for the on competition is the for a has been was by or and It is out for the not only to competition but also to the conditions, and even cooperation the with One with this is that the on competition is not that were at were in by and in by is an question whether on competition in were published with this is that the of competition in from the 1989). that the of mutualism to its no in and positive than negative interactions to the into The on on of and the and in to has out that ecologists during were more in competition and predation than ecologists The was being the and predation a ecologists in competition the in the data a interest in competition in the of than in the of during the is of predation only does data and only data on In fact, data the of and the of Fig. could be to that there were more articles on competition in the than in the during the period the be of modern interest in competition in ecology is in data It is that there is an in predation as which the above does not of the is in and in that ecologists were not in competition the be with the articles on ecology by the issue was how interactions maintained the of is on predation and competition communities and to and of the in the interactions as a impact on the of ecology at least in the I I not that than the for the dominance are and than one to of the could be as than I have that and in to and the theoretical of ecology in the and is an of to the and and the research was there be the dominance of competition and predation in its to be in the of data collected from journals covering diverse of ecology. the dominance even if competition and predation are not more than the to what be about to and

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