It is well known that sponges constitute one of the most prevalent groups in marine benthic communities based on their challenging structural organization, abundance and diversity, and their functional roles in natural communities. The evolutionary success of this group may be explained by the close interaction between sponges and microbes, which dates back to the Precambrian era. This particular symbiosis has become a key factor within sponge research and is an emerging topic of two scientific disciplines: chemical and microbial ecology. This mini-review evaluates the influence of these two disciplines on the general scientific community using a series of bibliometric indicators to ensure objectivity. Our analyses showed that, although sponge chemical ecology has a greater overall impact on the scientific community, both disciplines are cited equally and more frequently than expected. Both research areas show a great impact on applied sciences, but the ecological perspectives of sponge chemistry and microbiology may fall outside the interests of a broader ecological audience. Moreover, we highlight some research topics (e.g. effects of environmental stress) that may require further attention. Hence, sponge chemical and microbial ecology have the opportunity to contribute to broader ecological issues in topics that make sponges particularly important, such as symbiosis.
Las esponjas constituyen uno de los grupos predominantes en las comunidades bentónicas marinas gracias a su potencial organización estructural, abundancia, diversidad y a las funciones que desempeñan en las comunidades naturales. El éxito evolutivo de este grupo yace en la estrecha interacción con microorganismos que data del Precámbrico. Esta particular simbiosis se ha convertido en un factor clave en la investigación sobre esponjas y está emergiendo en dos campos como el de la ecología química y microbiana. Esta mini-revisión evalúa la influencia de estas dos disciplinas en la comunidad científica utilizando una serie de indicadores bibliométricos para asegurar la objetividad. Nuestro análisis muestra que aunque la ecología química presenta un mayor impacto global, ambos campos son citados de manera similar y con una frecuencia superior a la esperada. Ambas áreas presentan un gran impacto en ciencias aplicadas, pero las perspectivas ecológicas de las dos disciplinas científicas deben quedar fuera de los intereses generales de la comunidad de ecólogos. Además, señalamos algunas áreas (e.g. efectos del estrés ambiental) que necesitarían mayor atención. Por tanto, la ecología química y microbiana de esponjas tienen la oportunidad de contribuir sobre cuestiones de ecología general con temas que las hace particularmente relevantes, como es la simbiosis.
Phylum Porifera (Grant, 1836) are sessile metazoans with a differentiated inhalant and exhalant aquiferous system with external pores. A unidirectional water current is generated through the body to accomplish physiological functions by flagellated cells (choanocytes), usually contained within chambers (
One of the keys of the evolutionary success of this group lies in the close association between sponges and microbes, which dates back to the Precambrian era (
Since many studies of sponge chemistry and microbiology have documented a huge chemical (
In sponge microbial ecology, several dozen papers also evidence the connection between associated microorganisms and natural products (
Can we go beyond highlighting topics that have received or require considerable attention to assess the impact of these topics on the scientific community? Who is interested in these topics? Only sponge lovers, or are they important outside the sponge research community? Do they contribute to general ecological and microbial theory, or what are the biotechnological implications? This mini-review analyses literature trends in sponge chemical and microbial ecology (i.e. papers on the interactions among sponge chemicals or sponge microbes and their environment) from the early stages of these research lines until 2014. Our goal is to help identify the audience and impact of these research lines, which can result in improved research questions, better journal selection and increased repercussion of these topics. Some book chapters and reviews published in the literature in the last four to five years exhaustively compile and analyse papers in both sponge ecology areas: chemistry (
Revising all chemical and microbial ecology literature on sponges can be a challenging task. Since the appearance of the Web of Knowledge (
For an evaluation of the literature on sponge chemical and microbial ecology we used the same criteria described by
We used several indicators to compare the chemical and microbial literature. We recorded the total number of papers, the total number of citations, the average number of citations per publication (i.e. mean citation rate, MCR), the total number of citing papers and the h-index
We wanted to complement the h-index with three other bibliometric indicators to estimate the overall and average scientific impact of two research fields. We calculated the highly cited papers (HCP) indicator, the aggregate of the natural logarithm of citations of each publication (AC), and the mean normalized citation score (MNCS) indicator. The HCP indicator, which behaves similarly to the h-index, counts the number of papers with at least a certain number of citations (
The Science Citation Index Expanded database provides results as a function of Authors, Subject Categories and Journals, which allows quantitative examination of the research output by contributing researchers, disciplines and scientific journals. Subject categories are non-exclusive, so a single paper may be included in several disciplines. Consequently, by adding up the number of papers or percentages for each category, we obtain a number larger than the actual number of records found or percentages larger than 100%. For details on what is comprised in each subject category, see the webpage (Scope Notes, Science Citation Index Expanded). From the Web of Knowledge (
A total of 312 papers initially met the sponge chemical ecology requirements, while 190 papers were found with the microbial ecology search. After checking all published works, 82 papers of the chemical search and 59 papers of the microbial output were completely unrelated to our goal and did not meet our definition of sponge chemical and microbial ecology so, they were discarded. We found an additional publication (
Sponge chemical ecology ranked first in terms of productivity (i.e. number of papers), almost doubling the number of papers published in microbial ecology (
Sponge research area | n | cites | MCR | art | h | HCP | ACa | MNCSb |
---|---|---|---|---|---|---|---|---|
Chemical ecology | 231 | 6997 | 30.29 | 4099 | 44 | 71 | 631.43 | 3.13 |
Articles | 184 | 4187 | 22.76 | - | 36 | 66 | 478.73 | 2.28 |
Reviews | 43 | 2807 | 65.28 | - | 24 | 12 | 148.04 | 8.35 |
Microbial ecology | 131 | 4408 | 33.65 | 2498 | 35 | 36 | 348.84 | 2.25 |
Articles | 103 | 2927 | 28.42 | - | 29 | 30 | 263.17 | 2.06 |
Reviews | 26 | 1442 | 55.46 | - | 14 | 8 | 79.73 | 3.61 |
a, ;
b, , where n denotes the number of papers of the research field, ci denotes the number of citations of the ith publication, and ei denotes the average number of citations of all papers in the year in which the ith publication appeared.
Of the 231 papers in the chemical ecology field, 43 were reviews (18.6%). Almost the same percentage of reviews occurred in microbial ecology (19.8%). These reviews accounted for over 32% of the citations in both research areas (
According to our search and our selection criterion, the 231 papers on chemical ecology were contributed by 718 authors. Almost 20% of the researchers (129) had multiple contributions (two or more papers) and only 3.2% published five or more papers. The 131 papers on sponge microbial ecology were contributed by 445 researchers, 19% of them had multiple contributions, and just 1.6% had five or more papers.
Papers on sponge chemical and microbial ecology covered over 20 subject categories in the Web of Knowledge (31 and 26, respectively;
Subject category | Chemical ecology | Microbial ecology | ||||
---|---|---|---|---|---|---|
n | % | h | n | % | h | |
87 | 37.7 (1) | 28 | 41 | 31.3 (2) | 16 | |
64 | 27.7 (2) | 24 | 29 | 22.1 (3) | 13 | |
35 | 15.2 (3) | 19 | 4 | 3.1 (9) | 4 | |
29 | 12.6 (4) | 15 | 10 | 7.6 (6) | 5 | |
26 | 11.3 (5) | 14 | 14 | 10.7 (5) | 9 | |
19 | 8.2 (6) | 8 | 16 | 12.2 (4) | 7 | |
15 | 6.5 (7) | 11 | 4 | 3.1 (10) | 4 | |
14 | 6.1 (8) | 11 | 45 | 34.4 (1) | 21 | |
13 | 5.6 (9) | 9 | 8 | 6.1 (7) | 6 | |
13 | 5.6 (10) | 10 | - | - | - | |
12 | 5.2 (11) | 8 | 3 | 2.3 (12) | 3 | |
12 | 5.2 (12) | 9 | - | - | - | |
11 | 4.8 (13) | 9 | 7 | 5.3 (8) | 7 | |
8 | 3.5 (14) | 6 | - | - | - | |
6 | 2.6 (15) | 6 | 1 | 0.8 (15) | 1 | |
6 | 2.6 (16) | 4 | 2 | 1.5 (13) | 2 | |
5 | 2.5 (17) | 5 | - | - | - | |
4 | 1.7 (18) | 3 | 1 | 0.8 (16) | 1 | |
3 | 1.3 (19) | 3 | 2 | 1.5 (14) | 1 | |
3 | 1.3 (20) | 2 | 1 | 0.8 (17) | 1 | |
2 | 0.9 (21) | 2 | 4 | 3.1 (11) | 3 | |
2 | 0.9 (22) | 2 | 1 | 0.8 (18) | 1 | |
2 | 0.9 (23) | 2 | - | - | - | |
1 | 0.4 (24) | 1 | 1 | 0.8 (19) | 1 | |
1 | 0.4 (25) | 1 | 1 | 0.8 (20) | 1 | |
1 | 0.4 (26) | 1 | - | - | - | |
1 | 0.4 (27) | 1 | - | - | - | |
1 | 0.4 (28) | 1 | - | - | - | |
1 | 0.4 (29) | 0 | 1 | 0.8 (21) | 0 | |
1 | 0.4 (30) | 0 | - | - | - | |
1 | 0.4 (31) | 0 | - | - | - | |
- | - | - | 1 | 0.8 (22) | 1 | |
- | - | - | 1 | 0.8 (23) | 1 | |
- | - | - | 1 | 0.8 (24) | 1 | |
- | - | - | 1 | 0.8 (25) | 1 | |
- | - | - | 1 | 0.8 (26) | 1 |
Over 4000 papers representing 107 subject categories cited the 231 papers on sponge chemical ecology, whereas the 131 records published on microbial ecology were cited by almost 2500 papers that represented 100 categories. This large number of subject categories compared with the relatively low number of categories that represented the chemical and microbial research output (i.e. around 29) implies a great interest in sponge chemical and microbial ecology not only among the scientific community in the same research area but also in other scientific disciplines. Considering those categories, which represented over 10% of papers on chemical ecology and papers that cited them, a goodness of fit (
The
Overall, the 231 and 131 papers on sponge chemical and microbial ecology were published in 103 and 69 journals, respectively. Most of them have published one single paper on either of the two research areas and the top 10 journals account for around 40% of all papers in both disciplines (
Journal | n | % | cum |
---|---|---|---|
Chemical ecology | |||
16 | 6.9 | 6.9 | |
15 | 6.5 | 13.4 | |
14 | 6.1 | 19.5 | |
9 | 3.9 | 23.4 | |
8 | 3.5 | 26.8 | |
7 | 3.0 | 29.9 | |
6 | 2.6 | 32.5 | |
6 | 2.6 | 35.1 | |
5 | 2.2 | 37.2 | |
5 | 2.2 | 39.4 | |
Microbial ecology | |||
10 | 7.6 | 7.6 | |
8 | 6.1 | 13.7 | |
7 | 5.3 | 19.1 | |
6 | 4.6 | 23.7 | |
5 | 3.8 | 27.5 | |
5 | 3.8 | 31.3 | |
4 | 3.1 | 34.4 | |
4 | 3.1 | 37.4 | |
4 | 3.1 | 40.5 | |
4 | 3.1 | 43.5 |
We looked at the impact of sponge chemical and microbial ecology on the scientific community. To do so, we quantitatively analysed references published on these research areas gathered within the Science Citation Index Expanded database. This quantitative analysis provides a historical view of these two disciplines over the years, a current diagnose of their status, and opportunities to take full advantage of the existing literature and to improve future research on these topics.
According to our search history and selection criterion, literature on sponge chemical and microbial ecology appeared during the 1970s. Despite the simultaneous appearance of both sponge research areas, chemical ecology started growing a little bit earlier and has shown a gradual increase since the 1990s; its overall impact, evaluated by a variety of bibliometric indicators, seems to be greater than those of microbial ecology. However, the average impact of papers from both disciplines evaluated by the MNCS indicator is quite similar. Although the h-index seems to show some theoretical inconsistency (
Reviews are crucial and useful tools for collecting information and updating the status of a particular research field. Around 20% of the papers on sponge chemical and microbial ecology were reviews, which is about twice the percentage of reviews in the broader field of sponge ecology (9.8%, updated to 2014 from (
A huge impact on the scientific community is derived from the large number of subject categories that cited papers on sponge chemical and microbial ecology. Chemical ecology research on sponges is highly cited by the categories
Surprisingly, there is a lower number of citations than expected from the subject categories
Further evidence suggests that sponge chemical ecology contributes little to the broader field of ecology. Although the journals from the
Sponges are considered an ecologically important group in marine benthic communities (
Overall, chemical and microbial ecology in sponges are disciplines that share many areas, both contributing to our understanding of host-symbiont interactions, areas that have proved useful for applied sciences. However, an extra effort is needed to make progress on fundamental ecological issues such as the role of sponge symbioses in population dynamics and community organization (
We thank N. Webster and D. Sipkema for their comments and suggestions on a previous version of the manuscript. We also thank the anonymous reviewer for his/her valuable remarks. This research is part of the PhD thesis of OSS, who was supported by a CSIC pre-doctoral grant. The research was funded by the Spanish government (SOLID: CTM2010-17755 and BENTHOMICS: CTM2010-22218) and is a contribution of the Consolidated Research Group "Grupo de Ecología Bentónica” (SGR2009-655) of the Catalan Government.