Morpho-plasticity in colony structure is an adaptive strategy upon which some coral species rely to take advantage of changes in their environment (Foster, 1979; Muko et al., 2000; Smith et al., 2007; Todd, 2008; Forsman et al., 2009). Hermatypic corals can adopt branching, massive, encrusting, columnar, laminar, foliaceous, nodular, and free-living (corallith) forms (Veron, 2000). However, morphologic variation may be present within not only a single species, but even within a single colony; such phenomena are typically in response to local environmental conditions, which influence coral growth and led to changes in skeletal architectures (Hughes, 1987; Lough and Barnes, 2000; Lough and Cooper, 2011). In general, the development of distinct morphotypes may be influenced by several exogenous factors, such as substrata type, depth, competition, space and light availability, bioturbation, and water dynamics (Glynn, 1974; Foster, 1979; Hughes, 1987; Van Veghel et al., 1996; D'Croz et al., 2001; Grigg, 2006; Smith et al., 2007; Tortolero-Langarica et al., 2016), as well as endogenous factors, such as the Symbiodinium assemblage and genetic variations (Van Veghel et al., 1996; D'Croz et al., 2001; Grigg, 2006; Smith et al., 2007; Todd, 2008; Forsman et al., 2009; Paz-García et al., 2009; Barshis et al., 2010; Boulay et al., 2012). The influence of all these factors may promote differences in the metabolic pathways that each species invest their energy resources, resulting in different skeletal characteristics in order to guarantee their continual growth and survival (Veron, 2000; Smith et al., 2007). Different colony forms not only benefit the species survival, but also contribute to the reef structure and complexity; such which increases in rugosity are associated with increased the biodiversity (Spalding et al., 2001; Alvarez-Filip et al., 2009).

One of the most abundant reef-building coral genera of the tropical Pacific Ocean is Porites, which normally adopts a massive growth form (Guzmán and Cortés, 1993; Glynn et al., 1994; Lough et al., 1999; Lough, 2008; Lough and Cooper, 2011). Poritid corals can be present in different morphotypes in the same reef area (Smith et al., 2007; Paz-García et al., 2009; López-Pérez, 2013). In addition, the nature of coral accretion in massive species is well understood and allows recognition of specific skeletal features, such as high and low density bands, over time (Lough and Barnes, 2000). Such banding patterns are typically assessed in conjunction with other growth parameters such as the skeletal extension rate (linear growth, in cm yr⁻¹), skeletal density (CaCO₃ bulk mass, in g cm⁻³), calcification rate (g cm⁻² yr⁻¹), and tissue thickness (depth of live tissue, in mm) (Knutson et al., 1972; Lough and Barnes, 2000; Carricart-Ganivet and Barnes, 2007). The sex of coral can also affect its growth and timing of density-band formation, due males and females invest in different proportions the energy available for physiological processes such as reproduction and calcification (Harrison, 2011; Carricart-Ganivet et al., 2013). In consequence, genders may present different annual growth parameters between them (Cabral-Tena et al., 2013). Therefore, the coral's genders may affect the interpretation of the environmental proxies bound within the skeleton (Carricart-Ganivet et al., 2013).

In the Eastern tropical Pacific (ETP), Porites lobata Dana 1846, is an important component of the structure of coral reef communities (Guzmán and Cortés, 1989; Glynn, 1994; Glynn and Ault, 2000). Despite the importance of morphologic and growth variability in the reef structure, limited studies have been performed on massive corals (Graus and MacIntyre, 1982; Tomascik, 1990; Van Veghel and Bosscher, 1995; Smith et al., 2007). These include the reported by Norzagaray-López et al. (2014) who found growth differences between columnar and encrusting colonies, nevertheless it is important to highlight that these differences were possibly biased by the effect of the gender and latitudinal gradients variations. To date, a comparison of the growth of different morphotypes including the gender effect in Poritid corals has not been undertaken, though it seems reasonable to speculate that columnar, massive and free-living forms may calcify at different rates in each specific gender. We hypothesized that columnar and massive forms attached to the substrata have major extension and calcification rates compared with mobile free-living colonies and higher rates in male colonies, due to their different strategies to invest calcification resources. In order to test this hypothesis, extension rate, skeletal density and calcification rate were assessed using optical densitometry on three different morphotypes and gender of P. lobata. In addition, tissue thickness and time of formation of both high and low density-bands among the morphotypes and genders were documented and compared.

Coral parameters resulted from 80 pairs of density bands over a 6 years interval. P. lobata present a mean extension rate of 0.57 ± 0.03 cm yr⁻¹, a mean density of 1.17 ± 0.02 g cm⁻³, and a mean calcification rate of 0.65 ± 0.03 g cm⁻² yr⁻¹. At temporal level growth parameters does not showed differences (P > 0.05) over the 6 years analyzed (Table 1). However, growth metrics were significant different between coralliths, massive and columnar forms: in extension rate (H = 13.523, P = 0.001), skeletal density (H = 33.026, P < 0.001), and calcification rate (H = 6.444, P = 0.040; Figure 3). Columnar colonies showed an average of 33 and 15% lower rates in extension and calcification among the morphotypes. The gender was identified only for columnar and coralliths forms, massive colonies not showed evidence of sex gametes. Analysis of growth parameters between males and females colonies resulted in similar growth parameters when gender data pooled (Table 2). However, this was statistical different using the effect of morphotype and gender in extension and calcification rates (P < 0.01; Table 3), males colonies grew 30 and 40% faster than females for columnar and corallith morphologies, respectively (Figure 4). There was a positive relationship between extension and calcification rate (r² = 0.889, P < 0.001), but not between of skeletal density and calcification rate; in contrast, a weak relationship was found between extension rate and skeletal density (r² = −0.127, P = 0.001). Similar pattern were revealed when relationships were analyzed by morphotypes (Table 2).

Tissue thickness averaged 6.63 ± 0.14 mm for columnar growth forms, 7.78 ± 0.13 mm for massive and 7.32 ± 0.16 mm for coralliths, and these differences were statistically significant (H = 24.895, P < 0.001). There were gender differences of both columnar and corallith forms (Figure 5). The results reflects a 4–6 month differences in the apparent timing of density-band formation between morphotypes, this difference was displayed by the columnar forms with the lowest tissue thickness values compared to coralliths and massive (Table 2). In addition, a difference in the timing (months) of density-band formation among genders of P. lobata, with 5-month of difference for males, and 11 for females was observed. However, this was not consistent with the interaction effect between morphology and gender, where apparent timing of density- band formation was 2–3 month between genders in both columnar and corallith forms. These results indicate a stronger effect of the morphology with a 6-month difference in the apparent time of density-band formation between morphotype, even considering the colonies gender; where male and female coralliths showed faster extension, calcification rate, and thicker tissue compared with columnar colonies (Table 2).

Difference in calcification rate of distinct P. lobata morphotypes (Corallith, massive, and columnar) at the same depth range reveals the high plasticity of this scleractinian species and demonstrates that each morphotype grows at different rates, and such rates may depend on the colony's gender. Phenotypic plasticity has been reported for congeneric species in the central Pacific, which present different growth rates between distinct reef zones (e.g., high vs. low energy; Smith et al., 2007). Therefore, P. lobata appears to be able to readily modify their growth strategies, developing different forms and/or growing at different rates in order to persist over the reef framework.

All coral morphologies are distributed at the same depth range, but as expected, in different substrates. Columnar colonies of this study recruit to rocks and coral matrix, and is possible that they modify shapes depending of the complexity of the substrata and compete for space with other sessile species; when the available space is restricted coral growth could divert upward rather than sideward, promoting columnar forms (Van Veghel et al., 1996). Massive colonies were observed on calcareous platforms rounded by large sandy areas, a similar observation to that observed in the equatorial zone of the ETP (Guzmán, 1986). This particular shape allows the space separation >1 m, between colonies of the same form. It should be noted that massive growth forms tend to be larger and have higher in calcification rates compared with columnar and corallith forms. Therefore, massive forms are lesser extent by space and competition and may grow in both height and width, developing large colonies. The free-living (mobile) coralliths were found across flat, rocky areas between adjacent coral matrices. Then tended to develop rounded shapes due to interactions with coral reef fish and water energy. As the coralliths increase in diameter and weight, their morphology is ultimately subject to change over the time as they attach to the substrate (Glynn, 1974; Tortolero-Langarica et al., 2016).

The mean annual extension and calcification rates of P. lobata documented herein are the lowest (on average ~2-fold lower) documented for Porites genera across the Pacific Ocean (Guzmán and Cortés, 1989; Glynn et al., 1996; Lough et al., 1999; Lough and Barnes, 2000; Smith et al., 2007; Lough, 2008). Nevertheless, the range of extension values is similar to those of Porites species at the same latitude (Lough and Barnes, 2000). The upward growth and calcification rate of P. lobata corals from the eastern Pacific tend to decrease with increasing latitude, which is a similar pattern to that observed in massive Porites corals from the western Pacific (Lough and Barnes, 2000; Cooper et al., 2008). This may be influenced by the variability of the environment conditions at higher latitudes; for instance temperature and light decreases and higher nutrient load may inhibit or reduce coral growth, leading to lower extension, and calcification rates in corals of the sub-tropical latitudes of the ETP in comparison to conspecifics from tropical latitudes (Grigg, 1981; Risk and Sammarco, 1991; Lough and Barnes, 2000; Kessler, 2006; Pennington et al., 2006; Pantoja et al., 2012).

Differences in extension and calcification rates were observed between morphotypes, with columnar colonies presented the lowest rates compared with coralliths and massive (Table 2). Therefore, we reject the hypothesis that free-living coralliths may show slower rates compared with columnar and massive shapes. This may be explained because morphology forms of the same species can present different characteristics as a physiological response to intra-specific interactions for competition of habitat and resources (Van Veghel et al., 1996). These interactions may produce damage on coral tissue and erosion on the skeletal structure, generating a negative effect on extension and calcification rates (Carricart-Ganivet, 2007). Therefore, the organisms invest the energetic resources on tissue repair instead on growth.

In contrast with extension and calcification rates, skeletal density values of P. lobata are within the same range as those documented across the Pacific (Risk and Sammarco, 1991; Lough and Barnes, 2000; Carricart-Ganivet, 2007; Lough, 2008). At the population level, skeletal density is expected to be influenced by local environmental factors such as depth, nutrient load, sedimentation, light, water flux and pH (Grigg, 1982; Hughes, 1987; Risk and Sammarco, 1991; Lough and Barnes, 2000; Smith et al., 2007). Despite overall similarities in average levels with those documented in of the Pacific, differences between morphotypes were observed at IINP. Indeed, it is unsurprising that different morphologies' surface area/volume ratios could necessitate differences in density (Risk and Sammarco, 1991; Grigg, 2006; Smith et al., 2007; Lough and Cooper, 2011; Tortolero-Langarica et al., 2016).

Differences between genders were documented both herein and previously founded (Cabral-Tena et al., 2013; Carricart-Ganivet et al., 2013). Males in columnar and corallith morphotypes present higher growth rates than female colonies. On average, a coral colony invests ~15% of its daily energy budget on reproduction (Sheppard et al., 2009), with a high energetic cost to produce eggs than sperm (Harrison, 1985). Brooding corals produces in asynchronic maturation many oocites per year (Rodríguez-Troncoso et al., 2011). Therefore, female colonies continuously invest energy during their reproductive periods reducing the amount of energy available for calcification (Harrison and Wallace, 1990). As P. lobata is characterized as a gonochoric brooder coral (Harrison, 2011), it seems likely that female colonies will decrease their growth to a greater extent than males during periods of the gametogenesis, thereby generating differences in calcification rates between genders (Figure 4). Also, this is confirmed by the differences in tissue thickness between genders (Figure 5), where males typically present a greater thickness than females (Carricart-Ganivet et al., 2013), and this is including herein for most morphotypes. Therefore, both gender and morphotype appear to affect the growth of P. lobata.

P. lobata showed a similar HD banded pattern between morphotypes during the summer season. However, results differed between morphotypes when apparent timing of density bands deposition was examined. The difference between actual and apparent HD banding is an average of 6 months. Herein HD bands begin to form during the late winter when the SST begins to increase gradually (Lough and Barnes, 2000). Then, they continue to form until the end of the summer season 6 months later. This is due to the porous nature Poritid skeletons, a characteristic that allows continuing depositing calcium carbonate under the tissue layer (Barnes and Lough, 1992, 1993; Carricart-Ganivet et al., 2013; Tortolero-Langarica et al., 2016).

This study has demonstrated difference in extension rate, skeletal density, and calcification rates between different P. lobata morphotypes and genders. P. lobata is highly phenotypically plastic (Smith et al., 2007) and is found in both the Eastern and Western Pacific, despite a barrier to gene flow across the Eastern Pacific Ocean (Baums et al., 2012). This widespread distribution suggests a marked ability to adapt or acclimatize to a wide variety of environment. Indeed, this characteristic helps to the species to maintain their distribution over the coral reef framework and serve as a framework building species in the reefs of the ETP region. In addition, the variability in growth parameters suggests that colony morphology may factor into local and regional comparison. This must be considered, for instance, because due morphological variation itself may mask growth difference between coral communities. Therefore, we recommended that, are growth comparisons to be made between localities or over the time, the same morphologies are compared against each other.

JT, AR, AC, JC have substantial contribution con the concept and design of the work, and also with the acquisition, analysis and interpretation of the data; JT, AR, JC, AM contribute with the draft of the word and revise the intellectual content; AR approve the final version of the manuscript. Finally, JT, AR, AC, JC, AM agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of the work are appropriately investigated and resolved.